Arizona Beauty

Desert plants are the aristocrats of the plant kingdom. Their family tree records an unbroken line of evolutionary progress from that ancient time when all plants lived wholly or partially submerged in water. It is a chronicle of continuous battle against adversity as they moved out to inhabit the dry land areas of the earth. Fossil remains of the many who perished show us how bitter was the fight against the forces of drought and desiccation. But their evolution has progressed so far that today they are not to be pitied as individuals eking out a miserable and precarious existence in a barren and unfriendly environment. They are all highly successful species, living out full and fruitful lives.

To get a real appreciation of the problems which confront desert plants we should devote a little time to a consideration of the basic life problems of any plant. Water and food are its most immediate and fundamental needs. The first and simplest food manufactured by a green plant is a form of simple sugar. This results from a combining of carbon dioxide gas from the air with water brought into the cells from the roots or other absorptive surfaces. The energy necessary for this chemical transformation is supplied in some mysterious way when sunlight strikes the green pigment of the leaves or other green tissues of the plant. In the earliest beginnings of life on the earth all green plants were wholly or partially submerged in water. The unlimited abundance of water, carbon dioxide, dissolved mineral salts, oxygen and sunshine made their life the most complete picture of uneventful security which the world has ever afforded. It was only when plants began to move out of their aquatic or semi-aquatic habitat that the problems of life became acute and interesting. A plant whose leaves or other green tissues are exposed to the air is forced to lose water by evaporation whenever it takes in the atmospheric carbon dioxide neccessary for food manufacture. No scheme has yet been worked out to upset this inexorable balance. In the driest parts of the Arizona deserts there are heavy rains at times. Some desert plants live out their whole life span in a short space of time following a period of abundant rain. Others make active growth during periods of available moisture and then dry up and become completely dormant, waiting until water shall once more stir them into activity. Perhaps the most interesting of the desert plants are those which have developed a provision for rapid growth and reproduction during times of greatest moisture and then have some scheme for shifting the gears of life speed and traveling along in low when the water supply falls off. The ocotillo and palo verde, putting out leaves and flowers when moisture is abundant and dropping their leaves as soon as it becomes scarce, are possibly the best examples of this procedure. The small, peg-like leaves of the chollas and prickly pears, occurring at every cluster of spines on the young stem segments, undoubtedly increase the food manufacturing surface of the plant during the period of vegetative growth. but they fall off when the new stem joints are fully grown.

Another biological phenomenon which adds to the interest and understanding of desert plants is the fact that while they

may have very elaborate water storage devices, all their water reserve does not have to be in the form of liquid. When sugars or other carbohydrates are used up by plants or animals they are broken down into the simple chemical compounds from which they were originally elaborated, carbon dioxide and water. The amount of water thus liberated is not enough to take care of all the needs of the plant or animal, but it is an important contribution in times of water scarcity. This fact has been recognized during the present war in the consideration of diet for men exposed to the dangers of thirst. Sugar, to some degree, satisfies the water needs of the individual as well as furnishing food. The immense amount of starch and sugar stored in the stems and roots of many of the desert plants represents a very considerable supply of available water. An understanding of this principle will help explain some rather baflling phenomena. Ocotillo branches cut down in the fall or winter and piled up without contact with the soil may put out a full crop of leaves and blossoms next spring. Some of the water necessary for this activity must come from the oxidation of food stored within the stems.

Every one who sees the desert plants enjoys an appreciation of the beauty of their flowers and their peculiar habits of growth. A consideration of the simplest of these basic biological principles and how they have been applied will make one realize that these are something more than just peculiar plants with beautiful blossoms. They have the greatest record of accomplishment to be found in the plant kingdom. They have evolved furthest from their primitive aquatic beginnings. They are not just static vegetables sitting in the sun while they live out their allotted life spans, but are lively individuals who have worked out amazingly clever and efficient solutions to the problems of life on this rugged frontier so far removed from their original home. The desert plant lives an active and eventful life, beset with many of the same hazards and uncertainties which confront the animals in their struggle for existence. To those who know the story of plant progress, the lowliest desert species has a far greater power to catch and hold human interest than does the lush, leafy plant growing in regions of abundant rainfall and mild climate. The writer's biological interests have been largely botanical and the opportunity to get to the desert in the spring was a pleasure that had been anticipated for many years. Never failing sunshine, abundance and variety of species combined with the efficiency of modern photographic apparatus and technique made the experience most fruitful. An extensive series of natural color photographs of all phases of desert plant life was obtained to be used as classroom illustrative material in a region far removed from the Southwest. The interest and helpful cooperation of local people wherever the work was done made the experience doubly pleasant and doubly profitable.

The photographs which accompany this article are closeups, chosen at random from a series taken of the blossoms of cacti of Arizona and adjacent regions. They represent but a very few of the many hundreds of species which occur in this group but they will convey some idea of the beauty and variety. Cactus flowers show tremendous variation as we go from species to species. They range in size from a quarter of an inch to a foot in diameter; they are of all colors of the spectrum with the exception of blue; most of them bloom during the hours of brightest sunshine while some open only at night and close when sunlight strikes them; some are odorless while others have the most exotic and powerful perfumes of any of the plants. Most of them exhibit a delicate satiny petal texture which is seldom found elsewhere in the plant kingdom. This beauty and variety of blossoms and their peculiar and interesting habits of growth have made them favorites of amateur and professional gardeners the world over. Desert flowers make such satisfactory subjects for color photography that a few bits of advice as to procedure may not be amiss at this point. The results from a properly exposed color photograph are an accurate and graphic reproduction of the subject, but any one of a large number of possible errors can spoil the picture. Color film is far more exacting in its demands than is black and white film and one has but one chance to influence the final result, the preparation he makes previous to snapping the shutter. Once that is done the die is cast and no change can ever be made in the picture. In black and white work many errors of exposure or posing can be subsequently corrected by various film treatments or print control methods. Moreover, a departure from the optimum exposure of color film brings about a change in color values rather than a simple variation in density as is the case with black and white. The Eastman Kodak Company provides complete information and instruction concerning the use of its Kodachrome film and this literature should be studied thoroughly if best results are to be expected. Field experience has shown certain precautions to be of paramount importance. An accurate and sensitive light meter is absolutely essential for closeup work, at least. A tripod sturdy enough to hold the camera steady while relatively long exposures, required for closeup work, are made. The exposures should always be made through small diaphragm openings to provide maximum depth of focus and maximum sharpness. The ordinary camera lens is so designed as to give greatest sharpness of definition when focused at infinity. When used to give an image of one-third natural size or greater on the film, the lens has to be stepped down greatly to correct optical aberrations which begin to be apparent. All of the accompanying pictures were taken with the lens diaphragm set at f.22 and at speeds varying from onehalf to one-tenth of a second. A reflector to brighten up the shadow areas of the subject is an absolute must. Between the brightest and the darkest surfaces which color film will accurately reproduce there is but a four to one ratio of reflected light while with black and white film this ratio may be as great as 100 to 1. Brighten the shadows with light reflected from a white card or an aluminum foil covered card. When one gets close to the subject a compensation must be made in the exposure time to take care of the increased magnification. A natural sized image, for example, calls for a four times normal exposure. Any camera store can supply a cardboard, dial type calculator for a dime which will supply this information. A Kodachrome haze filter should be used at all times to filter out the ultraviolet light so abundant in the southwestern sunshine. Ultraviolet light, unless held back by a filter, imparts a lavender blue cast to color photographs. No change in exposure time is necessary with this filter. If the sky should be cloudy or the subject in complete shade it is best to use a Wratten 2A filter, which likewise holds back ultraviolet light but in addition filters out a small amount of the blue light which is too pronounced under such conditions. No exposure reduction from the recommended meter reading is necessary at elevations below 3000 feet, but at higher altitudes it may be advisable to give less exposure than the meter indicates. The amount of reduction will have to be arrived at pretty much through trial and error, but in general 1/3 to 1/2 normal exposure at 6000 feet or higher is about right. One final admonition, there must be no movement of the subject during closeup exposures. Motion as well as image size is increased as we bring the camera closer to the object and will invariably impart fuzziness or actual blur. Some of the accompanying prints are the result of at least fifteen minutes patient waiting until there was a lull in the otherwise pleasant breeze. Dark colored cord is a great help when used for guy lines to steady slender, swaying branches. Arizona is a photographer's paradise. It has unlimited wealth of subject matter and perfect light conditions. An enormous amount of picture taking has been done in the state already but there are unlimited new and unique subjects waiting to be recorded and any day of the year is an ideal day for a photographic expedition. The cameras, lenses and films which will be available for civilian use after the war are something for the amateur and professional alike to dream about. Plan to come to the Southwest and get acquainted with the abundant life found in the desert. Become familiar with the beauty of its flowers and the ways of life of its amazing plants. Take pictures of what you see so that when you must leave the region you can take something of it along with you. There will be too much you will have to leave behind but you will have the scarlet torch of the ocotillo, the golden flame of the palo verde, the gorgeous colors and textures of the cactus flowers. The list will be long but you can get them all. Should you miss something you can always hurry back and get it the next season.