Proceedings Library

In 1960 the senior author presented a report (8) to the Plant Propagators' Society describing experiences in propagating trees of the genus Pistacia, especially the fall-coloring shade tree Pistacia chinensis Bunge. Since then, there has been an upsurge of interest in California in the propagation, planting and growing of the pistachio nut of commerce, Pistacia vera L. Because of its timeliness, this paper will bring the subject of Pistacia propagation up-to-date.

Before planting, or when a poor stand is realized from a lot of seed, it is possible, in the laboratory, to examine the seed and determine whether it is dead or dormant. Various standard techniques may be used: the excised embryo test; or the seed can be allowed to fully imbibe water, then it can be cut and put into a

The International Airport in Los Angeles has taken advantage of this "tropical" thought association for commercial reasons: The winter traveler from Canada, from the blizzardy plains of the middle west, or the snowbound eastern states, is made to believe that he landed right in the tropics on stepping out of the plane into all the palms that wise and skillful landscape architects placed in and around the air terminal in groups and in groves.

Limitation of palm habitats and uses makes familiarity with this plant group non-existent to some and restricted to those of you from winter-cold and desert-dry areas. So, to understand our topic easier a few remarks on physiology and ecology may be in order. Palms are the plants most valued

JOLLY BATCHELLER: Bill, I saw something just last week that I think is most interesting. At the California nursery convention in Palm Springs I saw a new type of pot which I think is excellent. I'm not boosting a product but it answers questions that some of us have. Many of us use a "spaghetti" system for watering and there are many different ways to attach the end of the tube to the container. They vary from a little lead weight you drop in—to a spike that you put the tubing over; and these cost money. The tubing itself isn't too expensive but the little plugs are. Someone has come up with a better idea. I think it's real good. They have taken a plastic pot and they have made a bulge on the side of it. My perspective in drawing these is a little bit difficult, but taking a view from the top, here is a normal pot and on the edge

Until very recently most citrus varieties in Hawaii were grafted on Rough lemon rootstocks or were "air layered." Only very recently the citranges, Cleopatra mandarin, and sweet oranges have come into use as rootstocks. Trifoliate orange has not been used by nurserymen; it was believed to be too slow in growing, taking 3 or 4 years to reach grafting size. When lined out in the field it made almost no growth from September until the following April or May. The common explanation was that it needed winter chilling. Temperatures near sea level in Hawaii are seldom lower than 65° F. and average in the high 70's which is considered unlikely to be a limiting growth factor for citrus.

We subjected rootstocks to three

Early propagators quickly realized that one of the major problems which must be solved when propagating plants by cuttings is to control water loss. The bell jar provided one solution. It provided a restricted volume of air which could become quickly saturated with moisture, either from evaporation from the media, or from water vapor transpired by the cuttings. When the water vapor in the air surrounding the cuttings

Greenhouse trial with Liquidambar and Zea mays suggest that the greater growth of closely-space plants may largely be due to less movement. Height growth was reduced at least 50% by a daily, 30-econd period of trunk motion

Reference is made, of course, to the UC System of Producing Healthy Container Grown Plants. It is still available as Manual 23 from Agricultural Publications, University of California, Berkeley, California

The early development of suitable growing media for containers was greatly hampered by man's inability to recognize the

As I think back over the attitudes and philosophy of education as I perceived it in both Australia and in New Zealand, there is a great similarity to that found in Central Europe. It is quite distinct and different from that found in the United States, and one which I feel is better not only for the students but for the country as a whole. In both Australia and New Zealand it is recognized that all students are not college caliber and that all students do not learn either at the same rate or by the same means.

Our visit coincided with the

Vegetative propagation of desirable clones is becoming more and more practical as we apply our present knowledge to old rooting problems and learn to benefit from past experiences, such as we may learn at this meeting. Our mission-oriented research has permitted a few publications, so some of you already know of some of my work.

We may think of rooting as the result of expression of the interaction of root promoting and inhibiting factors metabolized within the plant itself. Production and concentration of such factors may be investigated by taking cuttings at various growth stages—before, during, or after a flush of growth. With the assistance of my class

The herbicides discussed here may not be currently labeled and recommended by the manufacturer, thus they should not be construed as recommendations by the University of California. Presently, there are few herbicides that are labeled for use in ornamental containers so I can only report research findings. In ground covers and plants in the landscape, several herbicides are available and have

Stocks of seed of horticultural and agricultural crop plants must possess germination characteristics which result in rapid germination of a high proportion of the seed to produce evenly distributed, evenly developed stands of plants. Amongst crop plants particular restrictions in the range of conditions which result in germination may limit the geographical range of the plant or determine particular procedures for its cultivation; for example, high temperature sensitivity of leek seed prevents germination in low latitudes or during the summer in higher ones, and the requirements of celery seed demand greenhouse conditions for successful germination in the spring.

Since it is possible to find dormancy mechanisms still restricting germination in seeds of a crop plant as ancient as the leek it is not surprising that such mechanisms should be present in the seeds of plants taken more recently into cultivation, such as hardy ornamental nursery stock, both shrubby and

Nature has provided many ways by which we can increase stocks of lily bulbs but the rate of increase by bulb division, as in Lilium hansonii, by bulblets below ground, as produced by L. speciosum, by the rhizomatous bulbs of L. pardalinum, or the stoloniferous bulbs of L. superbum, is far too slow for most of us. A few species and hybrids form bulbils in the leaf-axils at flowering time and, while these can be collected in quantity and grown on, the two main methods adopted for the propagation of lilies involve the use of bulb scales or of seed

Scales. That universally useful item—the polythene bag—has made propagation by scales so simple an operation that I need spend very little time in describing our method. We take our scales in late summer or autumn when the lifting and transplanting of lilies is normally taking place. We drop the scales into a polythene bag, shake them up with enough PCNB dust (Quintozene) to give them all a protective coating then add a

Acer campestre, A. cappadocicum, A. circinatum, A. crataegifolium, A. davidii, A. forrestii, A. ginnala, A. griseum, A. grosseri, A. grosseri var hersii, A. palmatum, A. palmatum ‘Atropurpureum’ A. pennsylvanicum, A. platanoides, A. pseudoplatanus, A. rufinerve and A. trautvetterii.

Source of seed. Collection of seed from local sources is desirable generally; not only is it possible to collect at the optimum time but the seed can be selected from trees with desirable characteristics.

Seed of a limited range of Acer species can be purchased, usually from foreign sources, but results from these are often variable. This variability can be attributed to the drying out of the seed coat which, in turn, leads to the embryo becoming completely dormant. The drying of the seed does not necessarily mean it will not germinate, but germination tends to be erratic.

Seed collection. Due to variability in the time of

The cuttings are rooted in old span-frames running north to south. The frames have heating cables with individual thermostats for temperature control. Prior to putting in the cuttings, these frames have a layer of sand over the cable, followed by one foot of leaves for drainage and for preventing the mixture from becoming too compacted and, finally, 6 inches of rooting medium, consisting of 75 % sharp sand and grit and 25 % medium Irish moss peat. The rooting medium is allowed to settle, given a drench of 1 % IBA, diluted to 25 c c per pint of water. One gallon of this mix is watered over about three square yards.

The

Few other ornamental shrubs or trees have such valuable attributes and, although ornamental Malus are primarily grown for their spring flowers, many are attractive at other times of the year. Some, for example Malus ×. purpurea ‘Lemoinei’ and M. tschonoskii, have interesting coloured foliage throughout the summer, while others have highly coloured fruit and foliage in the autumn.

The trees are usually sold after 3 or 4 years in the nursery as standards or half-standards. Seedling crab rootstocks are commonly used because propagation difficulties have increased when clonal rootstocks are used. The problems have taken the form of bud failures with some cultivars, while in others the growth rate has been unsatisfactory and dieback has been common.

One of the main factors causing

After grafting, the plants are potted as deeply as possible into 2½ in pots in John Innes seed compost, so that only the leaf and bud is left above the soil. The plants are set into a closed case with a bottom heat of 70–80° F. and watered well. After 2 or 3 weeks callus will form on the top of the stock and the bud

Stock

One way to overcome this problem is by root pruning the seedlings prior to the transplanting operation. In the past this was sometimes done by using a material toxic to roots in the bottom of the flat. Copper was most commonly used, either as a screen laid in the bottom of the flat, or by coating the flat heavily with copper naphthenate. This is effective in killing the growing point of the taproot, but there is a danger of getting an excess of copper into the seedlings, which could lead to various

The important advantages of low capital cost and labour saving come from the simplicity of the technique and I have tried, therefore, to maintain this simplicity wherever possible.

Tunnel construction. The Tunnel design is basically that widely used in Great Britain for protected strawberry cropping. The wire hoops which support the polythene are bent into the required shape (Fig. 1) on a former from lengths of galvanized wire (8 swg with a tensile strength of 50 ton/in ). The hoops are spaced 30 in. apart along the tunnel (Fig. 1). Polythene sheet 6 feet wide is tied to a stake at the end of the tunnel and stretched over the hoops. It is secured by lacing two lengths of polypropylene bailer twine under alternate loops on either side of the tunnel (Fig. 1

Propagation and Production. Well grown stock plants are covered by a frame light in March to protect the breaking buds on last year's growth. When several little shoots have two fully expanded leaves, the upper portion of the stem carrying them is removed to force the lower buds to break and be given similar treatment subsequently.

The shoots are pulled off and the remnant of last year's wood trimmed away; then, having dipped them in rooting powder and boxed up for the mist unit, rooting occurs quickly and potting-on may begin in 17 days. Rooting medium may be

Bench grafting of fruit trees has been practiced in this country only to a very limited extent but at Long Ashton interest in mechanizing this technique was aroused when considerable quantities were required for an experimental purpose.

Whilst grafting machines are available in Europe a certain amount of difficulty was encountered in the purchase of a suitable machine, therefore a purpose designed tool was constructed. Various types of "joint" could have been used but from carpentry experience a mortice and tenon is the easiest to manufacture yet probably the most efficient in

Why should it be necessary to consider any new techniques when the majority of ground-cover plants are very easy to propagate and usually make a profit, and when the small numbers now produced are sold at prices as high as those asked for the normal run of flowering shrubs or perennials? In answer, if ground-cover is to be mass-planted as it must be to be successful, the plants offered in Great Britain will have to come down in price to an equivalent level to that of bedding plants and they need to be

Treatments, comparing the effect upon a range of species of making a basal wound, either before or after auxin application, together with non-wounding, gave results of three main types which appeared to be in part related to the kind of auxin preparation used, rather than the species.

1. Wounding before auxin treatment was beneficial, with the suggestion that this was through improved uptake of IBA applied as a powder formulation.
2. Wounding before auxin treatment was also detrimental, usually when IBA was applied in a readily absorbed alcoholic solution, suggesting supra-optimal uptake through the wound.
3. With some subjects wounding was beneficial irrespective of the time of auxin application

The value of a better understanding of these processes is discussed relative to the need for achieving optimal conditions for propagation.

This study was made during my employment in the Ministry of Agriculture, Fisheries and Food when I was employed as a Horticultural Advisor. All the time studies referred to here were made on the nursery of Messrs. John Waterer Sons and Crisp and I would like to thank the management and staff for allowing me to undertake this work and to submit this paper to the I.P.P.S.

The reasons I chose to study bench grafting were that, as an area of work, it seemed to be unduly complex and time consuming in terms of output.

My objectives were to: (1) Eliminate unnecessary work; (2) To simplify the process; (3) To make it a more pleasant job; (4) To speed up work throughout.

The first question to be asked is—what is the end product? In this case, a grafted plant in a closed frame is required and all work must therefore be directed towards reducing the time taken to achieve this end; in so doing, one must eliminate or simplify the job elements. Any alternatives should be judged on

J. WELLS: There are a number of simple illustrations of the effect of taking cuttings from different places on the parent plant. Taxus cuspidata comes to mind; if you take a cutting from the side of the plant you get a spreading type plant. If you want an upright form (i.e. to continue the natural habit which is produced from seed) then you must take a terminal cutting. The same thing is true of a number of Piceas, and Picea abies ‘Nidiformis’ is, I believe, produced in that way. This is true of Sequoias also.

D. HARRIS: What has been said of the Japanese yew (Taxus cuspidata) is equally true of the Irish yew (Taxus baccata ‘Fastigiata’).

P. THODAY: It is interesting that all these examples belong to the Coniferae. I think that the effects are rather more subtle in the Angiosperms compared with the

Climate. Lilongwe is situated 14° south of the equator, at an altitude of 3,500 ft. Annual rainfall is about 33 in., almost all of which falls between late November and early April. Mean relative humidity during January–February is approximately 85%, falling steadily during the dry season to 52% in October.

Mean temperature throughout the day rises to 74° F. in November and falls to 59° F. in July. Occasional frosts are experienced during June–August. Mean surface wind speed is approximately 4 mph in January and February, increasing steadily during the dry season to reach over 7 mph in October. Climatic data is shown in Table 1.

Leaf fall of most trees begins in June and much vegetation is defoliated by August. Many shade trees and shelter belts are, therefore, ineffective

Unlike the French lilacs which are budded or grafted, S. vulgaris ‘Lavender Lady’ is normally propagated by softwood cuttings. This plant is not incompatible with the commonly used understocks such as Syringa vulgaris, Ligustrum, or Forsythia, but it is raised from cuttings because its growth is slower than that of these understocks and, if grafted, would result in extremely heavy suckering from the understock.

Success with the rooting of softwood cuttings of S. vulgaris ‘Lavender Lady’ at Armstrong Nurseries was unpredictable. Through experiments, a successful method was found which is described as follows:

Softwood cuttings are taken as soon as new spring growth was available which is in mid-March in Southern California. Nodal cuttings are taken and stuck into flats filled with a

We began taking the cuttings the first week in July and finished about the middle of August. We started taking the varieties that, in our experience, rooted more slowly first, and finished with the more easily rooted varieties.

The cuttings were in soft growth, but we cut them back far enough to get into the bark area that had begun to mature enough to change to their naturally brown color of firm wood. Then we made the basal cut and trimmed off the very tender tips, leaving about a 5 or 6 inch cutting. All cuttings were treated with Hormex

Early in the spring of the following year, we go in and cut the seedlings back to ground level. After secondary shoots start to appear and have made a growth of 5 or 6 inches, we take off all shoots except one. In early July or August depending on growing conditions, while the shoots are vigorously growing, we start to bud. The following year when new growth appears, we cut back to the eye and the budded tree takes over. It is extremely important to have good budwood with big eyes. In the spring we severely trim our stock trees from which we cut our buds so that they produce lush, plump buds. I cannot overemphasize the importance of good plump budwood.

Another successful method we use for budding Quercus is to go into a block of young Quercus palustris with a caliper of from 1 to 1½ inches and insert a top bud about 5 to 6 feet

It took our moderator, Zoph Warner, who was responsible for arranging this discussion, a great deal of persuasion to convince me that I ought to participate on this panel. Not only do I suffer from a liberal amount of stagefright when it comes to giving a talk, but I simply could not get excited about the subject: Propagating Experiences—Old and New.

I could not help but think that here we have a highly successful Plant Propagators' Society, which for the last 20 years has made great strides in promoting and discussing the newest techniques in the field of ornamental horticulture, and here am I trying my darndest just to keep up with them. How in the world can I tell you good people something that's really new in plant propagation?

And as far as old propagating experiences are concerned, here again it is all well

Now a word about the V. dentatum seedlings that we use. We always try to get a strong 1-year seedling, grafting size. The reason is that a 1-year seedling does not have as many sucker buds as a 2-year seedling or transplant. Before we start potting these seedlings we trim them and start to eliminate the danger of suckers

There is a great difference in the way they used to produce and the present methods. They were also more secretive about their work and the only exchange of information took place on Sunday morning either inside or outside the church. Location depended a lot on the type of sermon for that day.

Let's take the item — rhododendrons; making cuttings was unheard of, you had to graft them. That was done in the spring in cold frames under double glass. Sometimes with disastrous results, but there was no research or any other information available, and still they produced good saleable plants. A lot of

Surveying the stock available to us, we felt that only the best would do. Up to this time we bought what the supplier offered, often inferior varieties. European varieties, while being developed from the same source, are quite distinct from Asiatic varieties in that they are usually fully-double, large-flowered, often so heavy that the stems cannot carry the bloom which then is hidden by foliage.

Asiatic varieties, in contrast, are of semidouble to double types with stiffer stems which carry the flowers well above the foliage. There are exceptions to both rules of course.

Tree peonies (Paeonia suffruticosa) are usually propagated by grafting on well-branched roots of P. lactiflora, the herbaceous peony. Grafting commences toward the end of August.

Well, after a long trip you are usually tired and thirsty, so it is logical to feel that these plants are also tired and thirsty. Let's unpack them and see what they look like, and give them a drink of water; your preference of beverage might not give the results hoped for. Now that their thirst has been met let's put them in a shaded area protected from the wind for a day or two, so that they can become accustomed to normal light after having spent several days in nearly complete darkness. When you

Top grafting of Acer palmatum var. dissectum and Cornus florida ‘Welchii’ to many propagators may not be something new; however, the methods we use to propagate these two particular plants may be an improvement over the old methods.

The preparation of understocks are the same for both maples and dogwoods. We start by selecting our understocks in the spring. This is not always an easy task because the supply of straight, strong stems may be short. The propagator then has to select the best he can from what is available.

For maples the understocks should be tall enough so that when they are decapitated and ready to graft, the stem will be at least 18" tall and have a caliper of 3/16 inches or more. In my experiences stems grafted at 18 inches and up to 3 feet have made the best

Briefly, it is an economical method of taking advantage of all natural agencies that promote plant growth and rooting, namely high humidity, filtered sunlight and abundant soil moisture. The chamber is a lightly constructed frame of 1-inch cedar boards, 3'9" × 12", to which is fastened along one side a length of 40 inch width of jute burlap, 10 oz. grade. During the hot part of the day, this burlap cover is stretched over finishing nails along the opposite side of the wooden frame or chamber. When in this position no dry outside air or direct sunlight can enter the chamber except through the moist burlap.

Preparation of soil. Soil for the cutting beds is rubbed through a ¾ or 1

After 2 years of study the following herbicides, CIPC + PPG -124 at 8 lb ai / A, EPTC at 5 and 20 lb ai / A, CIPC at 8 lb ai / A, dichlobeml at 4 and 12 lb lb a i/A, and diphenamid at 20 lb ai / A when impregnated on milled pine bark mulch calculated to deliver the expressed rate when applied at a depth of ½ inch provided adequate control of both broadleaf and grass weed species for 150 days in container grown Rhododendron obtusum Planch var. amoenum Rehd ‘Hino Crimson’ (Hino Crimson azalea) and Japanese holly. Severe injury was observed on both container grown species from the use of dichlobenil at the 12 lb ai / A rate. EPTC at the 20 lb ai / A rate caused excessive injury to only the Hino Crimson azalea.

Studies conducted for 2 growing seasons showed that preemergent herbicide applications of the following materials, dichlobenil at 12 lb ai / A, trifluralin at 8 lb ai / A, EPTC at 5 and 20 lb ai / A, CIPC + PPG - 124 at 8 lb ai / A and diphenamid at 20 lb ai / A provided adequate broadleaf and grass weed control 163 days after application when employed on container-grown Rhododendron obtusum Planch var. amoenum Rehd. ‘Coral Bells’ (Coral Bells azalea) and Japanese holly EPTC at 20 lb ai / A caused excessive injury to the Coral Bells azalea, while dichlobenil at 12 lb ai / A severely injured both species.

Experience and observation have proven that a soil mix high in organic matter and with a fair amount of clay has several points in its favor. Increased water holding capacity reduces the frequency of irrigation and a reduction of fertilizer loss. This is most important when containerized plants are on display for sale. A growing medium containing some soil classified as loam, possessing 20 to 25% clay, permits the roots of certain container-grown plants to make ready entry into the surrounding soil when planted in the landscape. Also the clay fraction of the loam soil serves in holding exchangeable ions

The rooting medium was a 2:1:1 (v / v / v) mixture of sandy loam top soil, vermiculite, and peatmoss, sterilized at 82° C.

Collection of cuttings. Juvenile softwood cuttings taken in the middle of June in Dorset, Ontario, rooted between 65% and 89%. At this time cuttings had fully elongated bottom leaves while the apical meristem was in full growth. Cuttings taken in

I do not wish to imply in any way that the experiences that others have had were not valid because I am sure they were. I would also like to suggest that what worked for me may not work for another person or for another plant.

To give a little background regarding the crop environment, the plants were

A characteristic of the chemical is that it hydrolyzes readily to carbon dioxide and alcohol. The possibility of using the material as a sterilizing agent for greenhouse soils or plant propagation media seemed of interest and utility in view of its toxicity to fungi and the fact that its use would not give rise to residue problems as do other biocidal materials.

Baycovin or DEPC was first manufactured by Farbenfabriken Bayer A.G., Leverkusen, Germany. Its solubility in water is 0.6%, and in 96% ethyl alcohol 50% with hydrolysis. Baycovin is harmless to humans under most conditions of use

Quite a few years ago, when I was new at making cuttings and grafts I read all the material I could find on the subject of propagation. I was under the impression I should take cuttings and scions and use them in a very short time, certainly within several days. This would be fine if we were in a mild climate where we would be able to go to the field and take fresh propagation materials daily.

About 6 years ago I began to wonder about the difficulty we were encountering in gathering cuttings and scions in January, February and March to get fresh material for our use. Also some winters there was winter damage to the cuttings, showing up after these later

Pear seedlings are difficult to use in juvenility studies because of their genetic variability and because they are rather difficult to keep in active growth in the greenhouse

Columnar European aspen (Populus tremula L. ‘Erecta’) is a valuable columnar clone that has proven difficult to propagate. Many attempts, by the authors, to root softwood cuttings have resulted in less than 10% success. Despite its value as a hardy upright poplar for northern areas, propagation failures have prevented wide commercial acceptance of this clone.

Propagation failures have stimulated research into aspen clonal propagation by greenwood cuttings (1), adventitious etiolated cuttings from root cuttings (1, 3) and tissue culture (5, 6). While these techniques have been

This study was done in cooperation with Dr. Toshio Murashige who graciously invited me to work in his well-equipped, tissue-culture laboratories at the University of California, Riverside.

In the preparation of the plant the shoots were cut back to the tuber when it was found that all of these shoots were reproductive. The ideal stage for taking vegetative shoots was when the new

The development of a new cultivar by hybridization requires not only a minimum of 8–10 years for a shrub and many more years for a tree, but also a great expenditure of funds.

Some idea of the extent of variation in Canadian hemlock is brought out by the fact that through the years the Arnold Arboretum has received plants or propagating material of 280 clones. They were discovered in the woods or in nursery rows by contributors who considered them worthy of perpetuation at a botanical institution. A search of the Arboretum's records reveals that hemlock variants were being received in the infancy of this century-old organization. Some were named and others, as is the case with many received more recently, simply bore descriptive notations such as, "dense form","dense

C. laevigata is prevalent in the southern third of Illinois, though not native around Urbana. There at the upper edge of Zone 6a, C. laevigata trees from at least two sources have proved hardy over a period of 15 years, and

One of the biggest problems has been the effect of air pollution on the trees. Monterey pine trees vary considerably in their susceptibility to air pollution, ranging all the way from no damage to, in a few cases, death of the tree. Most of the susceptible trees show a yellow mottling of the needles and, occasionally, will turn brown immediately after a heavy attack. This problem led to the study of the rooting of cuttings from resistant trees to see if clones could be developed that would be resistant to air pollution. As we studied the variability among Monterey pine seedlings, we discovered that an occasional tree would grow into an almost perfect Christmas tree shape with very little pruning. Some of these trees also had desirable color and needle characteristics that made them very desirable for Christmas trees. We visited farms that had planted

MODERATOR SNYDER: We have several questions here, and though we seem to be few in number this evening what we lack in quantity we will make up for in quality. Many of these questions are directed to specific individuals and if they are not present, we will set them aside in the event that they may come in later in the meeting. The first question is for Bill Morsink. Did you sterilize the cuttings of Acersaccharum?

BILL MORSINK: We sterilized the soil in which they are stuck at 180° F and this is very important. If we do not sterilize the soil we get only about 20% rooting, whereas with sterilized soils using the right size cuttings we can get up to 90% rooting.

MODERATOR SNYDER: Do you treat the cuttings in any way with a fungicide?

BILL MORSINK: I tried a few of these materials, but I found that the sugar maple is extremely sensitive to many of these

The only sound was a gentle hiss as air passed through the adjustable louvers into the room, combined with a faint hum from the lights. This was all the sound that could be heard as women robed in white moved about silently inspecting the rows and rows of white plastic trays. From time to time they would stop to more closely inspect and manipulate one of the living creatures on the white trays.

The room was divided into two parts by a lightproof curtain. Half of the room was brilliantly lit from overhead lights. On the basis of the glow from each lamp one determines that at least two types were used. The other half of the room was dimly lit for part of the time, in darkness the remainder. Every 12 hours, the curtains automatically parted and the lights moved to the dark side.

Resulting from our changing habits of living, we have developed