Mate Lib. AGRI U. S. DEPARTMENT OF AGRICULTURE. BUREAU OF PLANT INDUSTRY—BULLETIN NO. 53. B. T. (!ALL()\\ AY, Chief ( THE DATE PALM AND ITS UTILIZATION IN THE SOUTHWESTERN STATES, WALTER T. SWINGLE, PHYSIOLOGIST IN CHARGE OF LABORATORY OF PLANT LIFK HISTORY. VEGETABLE PATHOLOGICAL AND PHYSIOLOGICAL INVESTIGATIONS. TSS1KI> A I'KIL L'S, l!>04. WASHINGTON: G OV K H N M K N T I1 K I N T I N ( : < ' F 1 I •• I . BULLETINS OF THE BUREAU OF PLANT INDUSTRY. The Bureau of Plant Industry, which was organized. July 1, 1901, includes Vege- table Pathological and Physiological Investigations, Botanical Investigations and Experiments, Grass and Forage Plant Investigations, Pomological Investigations, and Experimental Gardens and Grounds, all of which were formerly separate Divisions, and also Seed and Plant Introduction and Distribution, the Arlington Experimental Farm, Tea Culture Investigations, and Domestic Sugar Investigations. Beginning with the date of organization of the Bureau, the several series of Bulle- tins of the various Divisions were discontinued, and all are now published as one series of the Bureau. A list of the Bulletins issued in the present series follows. Attention is directed to the fact that "the serial, scientific, and technical publica- tions of the United States Department of Agriculture are not for general distribution. All copies not required for official use are by law turned over to the Superintendent of Documents, who is empowered to sell them at cost." All applications for such publications should, therefore, be made to the Superintendent of Documents, Union Building, Washington, D. C. No. 1. The Relation of Lime and Magnesia to Plant Growth. I. Liming of Soils from a Physiological Standpoint. II. Experimental Study of the Relation of Lime and Magnesia to Plant Growth. 1901. Price, 10 cents. 2. Spermatogenesis and Fecundation of Zamia. 1901. Price, 20 cents. 3. Macaroni Wheats. 1901. Price, 20 cents. 4. Range Improvement in Arizona. (Cooperative Experiments with the Arizona Experiment Station. ) 1902. Price, 10 cents. 5. Seeds and Plants Imported Through the Section of Seed and Plant Intro- duction. Inventory No. 9, Nos. 4351-5500. 1902. Price, 10 cents. 6. A List of American Varieties of Peppers. 1902. Price, 10 cents. 7. The Algerian Durum Wheats: A Classified List, with Descriptions. 1902. Price, 15 cents. 8. A Collection of Economic and Other Fungi Prepared for Distribution. 1902. Price, 10 cents. 9. The North American Species of Spartina. 1902. Price, 10 cents. 10. Records of Seed Distribution and Cooperative Experiments with Grasses and Forage Plants. 1902. Price, 10 cents. 11. Johnson Grass: Report of Investigations Made During the Season of 1901. 1902. Price, 10 cents. 12. Stock Ranges of Northwestern California: Notes on the Grasses and Forage Plants and Range Conditions. 1902. Price, 15 cents. 13. Experiments in Range Improvement in Central Texas. 1902. Price, 10 cents. 14. The Decay of Timber and Methods of Preventing It. 1902. Price, 55 cents. 15. Forage Conditions on the Northern Border of the Great Basin. 1902. Price, 15 cents. 16. A Preliminary Study of the Germination of the Spores of Agaricus Campes- tris and Other Basidiomycetous Fungi. 1902. Price, 10 cents. 17. Some Diseases of the Cowpea: I. The Wilt Disease of the Cowpea and Its Control. II. A Cowpea Resistant to Root Knot (Heterodera Radicicola). 1902. Price, 10 cents. 18. Observations on the Mosaic Disease of Tobacco. 1902. Price, 15 cents. 19. Kentucky Bluegrass Seed: Harvesting, Curing, and Cleaning. 1902. Price, 10 cents. 20. Manufacture of Semolina and Macaroni. 1902. Price, 15 cents. [Continued 011 page 3 of cover.] Bui. 53, Bureau of Plant Industry, U. S. Dept. of Agriculture. PLATE I. OLD DATE PALMS AT HERMOSILLO, NORTHERN MEXICO. U. S. DEPARTMENT OF AGRICULTURE. BUREAU OF PLANT INDUSTRY—BULLETIN NO. 53. B. T. GALLOWAY, Chief of Bureau. THE DATE PALM ITS UTILIZATION IN THE SOUTHWESTERN STATES. WALTER T. SWINGLE, '( PHYSIOLOGIST IN CHARGE OF LABORATORY OF PLANT LIFE HISTORY. VEGETABLE PATHOLOGICAL AND PHYSIOLOGICAL INVESTIGATIONS. ISSUED APRIL 28, 1904. WASHINGTON: GOVERNMENT PRINTING OFFICE, 1904. BUREAU OF PLANT INDUSTRY. B. T. GALLOWAY, J. E. ROCKWELL, Editor. VEGETABLE PATHOLOGICAL AND PHYSIOLOGICAL INVESTIGATIONS. SCIENTIFIC STAFF. ALBERT F. WOODS, Pathologist and Physiologist. ERWIN F. SMITH, Pathologist in Charge of Laboratory of Plant Pathology. GEORGE T. MOORE, Physiologist in Charge of Laboratory of Plant Physiology. HERBERT J. WEBBER, Physiologist in Charge of Laboratory of Plant Breeding. WALTER T. SWINGLE, Physiologist in Charge of Laboratory of Plant Life History. NEWTON B. PIERCE, Pathologist in Charge of Pacific Coast Laboratory. M. B. WAITE, Pathologist in Charge of Investigations of Diseases of Orchard Fruits. MARK A. CARLETON, Cerealist in Charge of Cereal Investigations. HERMANN VON SCHRENK,« in Charge of Mississippi Valley Laboratory. P. H. ROLFS, Pathologist in Charge of Subtropical Laboratory. C. O. TOWNSEND, Pathologist in Charge of Sugar Beet Investigations. P. H. DORSETT, Pathologist. RODNEY H. TRUE, 6 Physiologist. T. H. KEARNEY, Physiologist, Plant Breedii CORNELIUS L. SHEAR, Pathologist. WILLIAM A. ORTON, Pathologist. W. M. SCOTT, Pathologist. JOSEPH S. CHAMBERLAIN, Physiological Chemist, Cereal Investigations. R. E. B. McKENNEY, Physiologist. FLORA W. PATTERSON, Mycologist. CHARLES P. HARTLEY, Assistant in Physiology, Plant Breeding. KARL F. KELLERMAN, Assistant in Physiology. DEANE B. SWINGLE, Assistant in Pathology. A. W. EDSON, Scientific Assistant, Plant Breeding. JESSE B. NORTON, Asswtantin Physiology, Plant Breeding. JAMES B. ROREI.,, Assistant 'itf Pathology. LLOYD S TE^NY ^Assistant in Pathofotft/. GEORGJ?^. HfcppcoCK, ^sistant in Pathology. PERLEY SPAULDING, Scientific Assistant. P. J. O'GARA, Scientific Assistant. A. D. SHAMEL, Scientific Assistant, Plant Breeding. T. RALPH ROBINSON, Scientific Assistant, Plant Physiology. FLORENCE HEDGES, Scientific Assistant, Bacteriology. CHARLES J. BRAND, Scientific Assistant in Physiology, Plant Life History. a Detailed to the Bureau of Forestry. b Detailed to Botanical Investigations and Experiments. ct LETTER OF TRANSMITTAL IT. S. DEPARTMENT OF AGRICULTURE, BUREAU OF PLANT INDUSTRY, OFFICE OF THE CHIEF, Washington, D. :> miles away, and from there to Algiers, some 390 miles by rail, with no packing except a little palm fiber about the bases. One box of these offshoots was packed in straw with no moisture whatever except from having been wet twice, once at Biskra and once at Algiers. So packed they were sent to New York by steamer, arriving July 3, then transshipped to New Orleans and finally carried by rail from New Orleans to Tempe, Ariz., where they arrived July IT. They were unpacked July 20, two months after they had been dug up. Prof. R. H. Forbes, under whose personal supervision the palms were planted and cared for, reports that the box of offshoots which had no packing other than the loose dry straw came through as well as those packed in damp moss or in charcoal. Some 80 per cent of these suckers lived. a It is very important that the offshoot be planted out high enough so that the growing bud in the center is never in danger of being covered with water when irrigated. (See fig. 6, p. 42.) In order to force the offshoots to take root and grow, the chief requi- site is that the ground be kept constantly wet about their bases. If the young plants dry out once they are lost, for the delicate new roots that are just forming will be killed. The Arabs water the offshoots every day for the first forty days after planting and then twice a week until winter, after which they are watered as often as may be necessary to keep the ground thoroughly moist. Another requisite almost as important as the keeping of the base of the plant moist while roots are starting is that the ground be warm when the offshoots are transplanted. It is useless to set out offshoots in autumn or winter; the best season is late in spring or early in summer, when the ground is thoroughly warm and when there is a long hot season after planting, permitting the young palms to become well established before winter. It is not necessary to shade the young offshoots, but they should be protected against cold during the first winter after being set out, by wrapping with burlap, heavy paper, or straw. Professor Forbes finds (see p. 10) that young seedlings are often killed by alkali where offshoots and old palms grow all right. Strong alkali is probably injurious also to offshoots just striking root, and the following method of preventing the rise of alkali, communi- cated })y Professor Forbes, may be advantageously followed in all cases where there is danger to be apprehended from this source: Throw up a high border on each side of the rows, running in both directions, thus creating a square inclosed space about each palm. This space ma}^ be flooded from the irrigating canals with fresh water, which carries away the salts accumulated near the surface down to « Forbes, R. H. Twelfth Annual Report, Arizona Experiment Station, p. 317. 22 THE DATE PALM. lower level beyond the reach of the young roots. The area about the ofl'shoot inclosed by the borders should then be covered with straw to a depth of a foot. This mulch will hinder evaporation and thereby restrict the rise of alkali, since each application of water washes the alkali down anew and the mulch continues to act as a check on evapo- ration. Such a method of planting should be adopted in those parts of the Salton Basin where there is danger of a rise of alkali from the subsoil. DISTANCES BETWEEN TREES. The Arabs almost invariably plant the date palm without any attempt at placing the young ofl'shoots in definite order. The result is, it is almost impossible for them to be sure of planting the trees at any con- stant distance from each other, some being close together, others wide apart, as can be seen in Plates XII and XIII. The unsystematic and frequently careless methods employed by the Arabs in the culture of the date palm can not be taken as models to be followed in introducing the date industry into the Southwest; we should rather follow the example of the French colonists in the Sahara, who plant the date palm in regular rows (see PL XVII, fig. 1), and have, as a rule, definitely planned and carefully executed systems of irriga- tion and drainage. Although the Arabs plant the date palms very close together, the French have found it advisable to place the trees wide apart, and many of the French colonists regret having placed the trees only 20 or 22 feet apart, their opinion now being that date palms should be planted from 26 to 33 feet from each other. Ben Chabat, an Arab, who is considered an authority on date cul- ture, makes two date palms speak together; one says to the other, " Take thy shadow away from mine and I will produce alone for us two together"0 — expressing the idea that too close planting is dangerous. At 26 feet apart, which may be taken as an average distance, about 60 palms would be planted on an acre. If the palms are put 30 feet or more apart other crops can be grown between the trees even when old. The amount of irrigation water available during the hot season and the value of land are factors which must be considered in deciding at what distance the offshoots should be planted. In general the far- ther apart the palms are, the more heat and light each receives, and the better and the more abundant is their fruit. Even when planted 26 feet apart or less there are, of course, large strips which lie unused between the palm trees for the first ten or twelve years after planting. It has become a common practice in the Algerian Sahara, copying to some extent after the Arabs, to plant garden or field crops between the trees until the palm trees become large enough to shade the ground. In case the soil is alkaline, it is "Masselot, F. Bui. Direction Agric. et Comm., Tunis, vol. 6 (1891), No. 19, PROPER PROPORTION OF MALE TREES. 23 f requently impossible to grow any crop until two or three years of abundant irrigation, coupled with a good system of drainage, have washed the alkali out of at least the top layers of the soil. Barley is usually the first crop grown on alkaline soil. After barley has been grown a year or two, the abundant irrigation being, of course, kept up, the land usually becomes freed from alkali sufficiently to permit horse beans, cowpeas, beets, and other garden crops, and, what is of more importance, alfalfa, to be grown. This Saharan alfalfa (see PL XVI, fig. 2), although refusing to grow on soil which produces a fair crop of barley, is, nevertheless, able to withstand without injury a percentage of alkali in the soil which would prevent the growth of ordinary alfalfa." PROPORTION OF MALE TREES THAT SHOULD BE PLANTED. It has been found in the date plantations of the Sahara that for every hundred date palms there should be at least one male tree to fur- nish pollen for use in fertilizing the flower clusters in spring. There is already a large number of male date palms in Arizona and Cali- fornia, so that it has not been thought necessary to introduce more than a very few from the Old World. The ratio of one male for every hundred female palms applies only in the Sahara, where it is possible to secure male palms known to flower at the right time to be used in pollinating. It often happens that many of the seedling male plants flower too late to be of any use. b It does not interfere so much with the usefulness of a male date palm to have it bloom too earty, since the bunch of male flowers can be preserved for some weeks without serious deterioration. In view of these facts it will be advisable in starting any plantations to put out at least one male palm for every fifty females, or better, one male for every twenty-five females. It will be desirable also to secure offshoots from different male trees in order to avoid getting male trees all of one kind, which might be found to bloom at the wrong season. In case no offshoots of male trees can be secured, a few seeds may be planted and the male palms saved to furnish pollen. When the trees begin to flower it will be possi- ble to see readily which male trees flower at the right season; the others can be destroyed and offshoots from female trees planted in their places. « After much correspondence with the Arab caids in the interior of the Sahara, a small quantity of the seed of this valuable alfalfa was obtained for the writer in the spring of 1901. It is earlier than ordinary alfalfa and resists heat and alkali better. It has been planted in the Cooperative Date Garden at Ternpe, Ariz., and it is hoped that it will prove as valuable in the Southwest as it is in the Sahara. & Out of six date palms which had flowered up to 1898 at the San Joaquin Valley substation of the California Experiment Station, three were female and three male, but two of the male palms did not flower until the female trees had ceased blooming. 24 THE DATE PALM. VARIETIES OF MALE DATE PALMS. Some male trees produce more pollen than others, and are much preferable to use in pollinating. When once good sorts of males are found they should be propagated by offshoots in the same manner as the female plants. In most parts of the Algerian Sahara no particular attention is paid to the propagation of suitable male palms, and in consequence pollen is sometimes scarce early in the flowering season and again later on, which often renders it necessary to procure pollen from neighboring orchards or even from other oases, sometimes at considerable trouble and expense. In Tunis there is a male variety propagated by offshoots called the Deglaoui used to pollinate late- blooming sorts. Another called the Dakar majahel was secured by Mr. D. G. Fairchild in Egypt, and has been sent to the Cooperative Date Garden at Tempe, Ariz. It is said to be the only male palm which produces pollen at the right time to be used on all of the eight varieties of female dates grown about Ramley, Eg}rpt. The chief requisite of a male date palm is that it shall produce an abundance of pollen at the right time to be used in pollinating the female sorts that are grown. If date palms were propagated from seed, and still more if any attempt should be made to breed new and better sorts, it would be very desirable to secure male sorts capable of transmitting desirable characteristics to their offspring. (See p. 20.) Schweinf urth has recently put forth the claim a that the male sort used for pollinating the flowers has a decided influence on the shape and, what is more important, on the size of the seed of the dates which result. If this were true it would be very important to secure male sorts which when used for pollination would produce small seeds. Schweinfurth's supposition is, however, without doubt erroneous, for in spite of his assertion that the observed variability of the seed in dates of the same variety b is a proof of the effect of the different sorts of pollen used to fertilize the flowers, the fact is that the seeds of any one sort are so uniform in size and shape as to furnish good characters for use in distinguishing varieties, and are regularly so employed by both Europeans and Arabs. The only part of the seed which could be affected directly by the male parent is the embryo, which in the date occupies so small a fraction of the bulk of the seed that it is not surprising that there is no observable effect of the pollen on the seed and much less on the pulp which surrounds it. a Schweinfurth, Dr. Georg. Ueber die Kultur der Dattelpalme. In Gartenflora, vol. 50, 1901, p. 513. & Naturally the seeds are not all exactly alike, even on the same tree, and some varieties of dates have seeds which vary appreciably in shape and even in size; but this range of variation is itself a varietal character. Of course the incorrect identifi- cations of dates often made offhand by the Arabs may easily lead to erroneous ideas as to the extent of variation in a sort through a confusion of varieties similar in external appearance, but differing in seed characters. CARE TO BE GIVEN TREES. 25 Male date palms generally have stouter trunks and more leafy crowns than female trees (see PL V, fig. 2), arid some have said that even the young plants could be distinguished — a matter of much im- portance where dates are propagated from seed, when it is desirable to recognize and destroy as soon as possible the superfluous male plants. It has not been found possible to depend on any of the signs given for distinguishing young male plants, and they can be recognized with certainty only when they are in flower. An inspection of figure 3 on Plate VII will show how different the male flowers are from the female and render it easy to determine the sex of the palms as soon as they show flowers. CARE TO BE GIVEN DATE PALMS. The chief care required by date palms is that they be irrigated as often as needful. The soil should be kept in a proper state of tilth, which is usually done by growing some crop between the rows, espe- cially when the palms are young. The leaves are trimmed off as they die, and care is taken not to allow too many offshoots to grow at the base of the stem, for they draw on the strength of the parent plant. In general not more than three or four offshoots should be allowed to grow at once. At least one should always be left attached to the mother plant to be used to replace it in case of accident. a Old palms, ten to fifteen years after planting, which have developed a good trunk 4 to 10 feet high, do not produce offshoots, and such trees require no attention other than the cutting away of the dead leaves, the pollination of the flowers, and the gathering of the fruit. THE AGE AT WHICH DATE PALMS BEGIN BEARING. The age at which palms come into bearing depends much upon the climate and soil; where planted in rich soil, watered abundantly, and where the summer heat is intense and long continued, the date may begin to fruit when very young. Trees have been known to bear in Arizona within four years after the seed was planted; however, such palms are too small to bear more than a very few fruits, and seedling trees are generally considered not to yield paying quantities of fruit until they are at least 6 or 8 years old (see Yearbook, 1900, PL LVII, fig. 1). When date culture is practiced scientifically, practically no seedlings are grown, but instead orchards are started by planting fairly large offshoots, which soon strike root, and which often bear «Many valuable seedling dates have been lost in this country because the suckers were kept closely trimmed off until the trees were in bearing. Only then was their value discovered after it was too late to propagate them. If an offshoot is always left attached at the base of the palm it may in turn be allowed to produce suckers after the parent plant ceases to produce them, and in this way a continuous supply of offshoots may be produced even at the base of old palms, and no variety need be lost. 26 THE DATE PALM. abundantly four or five years after being transplanted (see PL XXII). However, in the large plantations made in Algeria by the French col- onists it is not considered advisable to allow the palms grown from offshoots to bear fruit until five or six years after they are -set out, and the trees are not in full bearing until eight or ten years after they are planted. They continue bearing, if well cared for, until they are a hundred years or more old, a good tree producing an average of from 60 to 200 pounds of fruit a year," although some trees have been known to produce as much as 400 or 600 pounds6 when grown in rich soil and abundantly irrigated. The tree shown in a previous paper (Yearbook, 1900, PI. LVII, fig. 1) is a demonstration of the capabilities of Arizona as a date-producing country. It was only 8 years old from the seed when photographed, and yet bore some 400 pounds of dates. Again, an Amreeyah palm, grown from an offshoot imported by the Department of Agriculture from Egypt in 1889, yielded in 1900 over 300 pounds of dates (see Yearbook, 1900, PL LXII, fig. 1). A little palm growing on the grounds of the University of Arizona, at Tucson, where the winters are often cold, bore, never- theless, when it had been transplanted five years, two bunches of fruit weighing together some 30 pounds (see Yearbook, 1900, PL LVH, fig. 2). The large Deglet Noor palm growing at Biskra, Algeria, shown in the foreground of Plate LX, Yearbook, 1900, bore over 15 bunches of fruit, and the young Deglet Noor palm shown in Plate XXII, grown from a sucker set out only three years before, bore 3 bunches of fruit. POLLINATION OF THE DATE PALM. In a wild state the date palm is undoubtedly pollinated by the wind, and about one-half of the trees are males. It is probable that pollina- tion would be incomplete unless the proportion of male trees was something like one-half, for, although enormous quantities of pollen are produced, only a very small part of wind-blown pollen ever reaches the female flowers. The artificial pollination of the date palm was doubtless discovered by the ancient Ass}^rians, and has been practiced probably for three or four thousand years at least. Because of the great economy of pollen brought about by this practice, one male tree suffices to pollinate from fifty to a hundred females. The male flower cluster of the date palm consists of a stalk bearing «M. Masselot has published a list of all the important varieties of dates grown in the Tunisian Sahara (Bui. Direc. Agric. et Comm., Tunis, Vol. 6, No. 19, Apr., 1901), and gives the average yield per tree of 92 sorts. The Loozee variety has the lowest average yield, 55 pounds, and the Areshtee and Hamraya the highest, 220 pounds; the average yield of all the 92 varieties is 116.5 pounds per tree. ftln the oasis of Tebbes, the northernmost in Persia, it is reported that a full-grown tree may yield 200 man (of 3£ pounds). Bunge, Petermann's Mittheilungen, 1860, p. 214. POLLINATION. 27 a considerable number of short twigs to which the flowers are attached, the whole contained in a sheath at first entirely closed, but which finally ruptures, disclosing the flowers. (PI. VII, figs. 1 and 3.) The Arabs cut the male flower clusters from the trees shortly before the flowers have fully opened, at a somewhat earlier stage than shown in Plate VII, fig. 1. The separate twigs to which the male flowers are attached (PL VII, fig. 3, twig below) are from 4 to 6 inches long, and bear anywhere from 20 to 50 male flowers, each containing 6 anthers full of pollen. One of these twigs suffices to pollinate a whole female flower cluster, and to bring about the development of a bunch of dates. The female flowers, like the male, are borne inside of sheaths which are at fir^t entirely closed. Finally the sheath is split open by the growth of the flowers within (PI. VII, fig. 2, twig to left), and at this stage pollina- tion is accomplished. The two tips of the cracked-open sheath are separated and the cluster of female flowers pulled out. (PL VIII, fig. 3.) A twig of male flowers is then inserted into the cluster of female flowers and tied in place with a bit of palm leaf or with a string. (Fig. 2 and PL VIII, fig. 4.) This completes the operation of pollination. The fruit cluster soon begins to grow rapidlv, and in a few weeks the piece of palm fiber or thread with which the male flowers are held in place is broken by the pressure of the grow- ing fruit cluster. Such a fruit cluster, still confined, but which will shortly break the fiber, is shown in figure 1 (p. 16). In the Algerian Sahara the date begins to flower in April, and sometimes produces flower clusters as late as June 1. The female flower clusters, which may be from five to twenty in number on a single tree, are not all produced at the same time. It is necessary in consequence to pollinate each flower clus- ter as it appears, and sometimes an interval of several weeks elapses between the appearance of the first and last flower clusters, so the trees must be ascended several times. The Arabs are very expert in doing this work and seldom overlook a tree, even where the palms are planted without any order; indeed, they rarely miss even a single flower cluster. It requires some skill to climb a tall palm tree, as FIG. 2.— Date flower cluster after artificial pollination; a sprig of male flowers has been inserted among the female flowers and tied fast with a palm-leaf fiber. (One-third natural size.) From negative by the author. 28 THE DATE PALM. the trunk below is very smooth and it is difficult to pass between the stalks of the lower leaves in order to get at the flowers, since these leafstalks are armed with sharp, rigid thorns. (Fig. 1, p. 16.) The Algerians use no rope or other apparatus to ascend the trees, but climb up with their bare hands and feet. (PL VIII, figs. 1 and 2, and PI. XIII.) When date culture becomes an important industry in the South- western States it is probable that American ingenuity will devise meth- ods of simplifying the work of pollination. For example, it would be easy to find means of marking the trees, and also the flower clusters, to show which have been pollinated. It might be possible, for instance, to tie the male flowers in place with a bright-colored strip of cloth, which would make it easy to see whether all the flower clusters had been pollinated or not. It is possible that in some places Indians will be able to take the place of the Arabs and do this work efficiently. , It is absolute^ necessary to pollinate all the flowers in order to secure dates of a good quality, although the dates do not fall off. even if the flowers are not pollinated. About the end of June, by which time the fruits are of some size, three fruits will have developed from each flower. Then occurs a remarkable phenomenon. If the flowers have been pollinated, two of the three fruits fall, leaving a single date for each flower. If, on the contrary, the flowers have not been pollinated, all three dates remain attached and continue to grow, becoming closely crowded together and somewhat deformed. Such dates are without seeds, but never prop- erly mature, and are entirely valueless/' This peculiar behavior of the date palm enables the cultivator to tell by inspection which bunches have been pollinated and which have escaped attention, and the cutting away of the excess of bunches from too heavily laden trees should be postponed until this time, when it is possible to tell which bunches will mature perfect fruit. As a rule, only one or two clusters should be left on the young date palms which have just begun to bear, and only eight or ten even on old trees. Some varieties do not require much thinning, as they do not produce more bunches than they can nourish properly, whereas other sorts produce twice as many as the tree can support. It sometimes happens that some of the female flowers appear in spring before any of the male trees have blossomed. To provide a supply of pollen for such flowers the Arabs make a practice of keep- ing a few bunches of male flowers from the previous year, which are placed in tight paper bags and hung up in a cool, dry place. The pol- len is said to keep without deterioration for at least two years. The importance of securing male trees which flower at the right time has been noted on page 24. « Such unpollinated dates have sometimes been supposed by inexperienced observers to be a superior variety because of their seedlessness. GATHERING, CURING, AND PACKING DATES. 29 By an inspection of Plate VII, figure 3, it will be easy for those who possess seedling date palms to determine the sex of the plant as soon as any flowers are formed. Superfluous male trees can then be destroyed and replaced by female trees before they have reached a large size. In case of gardens where there are a few female date palms and no males available to furnish pollen, it will be necessary to secure pollen from a distance — not a difficult matter, since male flowers can be shipped anywhere without deterioration if protected against loss of pollen. After irrigation the labor of artificial pollination is the most impor- tant required in a date orchard. The irrigation, however, is very nearly such as would be given to any fruit trees, whereas the process of pollination is one that is not required by any other commonly cul- tivated tree. It should, however, be remembered that for the first ten or fifteen }^ears after date palms are planted the flowers are so near to the ground that artificial pollination is performed very easily. The operation becomes difficult only when the palms are old and verv tall. GATHERING, CURING, AND PACKING DATES. Some varieties of dates require practically no curing, being ready to pack and ship as soon as they have ripened. Other varieties, however, require some preparatory treatment. Dates are borne in bunches, which have a single stem with numerous slender twigs to which the fruits are attached. (Pis. IX and XXII.) A bunch carries from 10 to 40 pounds. It is very rare that all the dates on a bunch ripen at once, and in the case of choice varieties those which first ripen are fre- quently hand picked and shipped at once in order to get the high prices paid for the earliest shipments. It is also asserted that picking the outer dates of the bunch, which usually ripen first, permits the inner fruit to ripen better. Usually the whole bunch is cut off and hung up in a dry and shady place when most of these dates are ripe and the remainder beginning to ripen. It has been found necessary to remove any dates which have begun to spoil before the bunches are hung up, for if such dates are left the whole bunch may spoil. Usu- ally within a week or two all of the dates ripen, a and the bunch is ready for shipment. The choice varieties of dates are shipped from the Sahara either in bags or more often in long wooden boxes. They are afterwards «In case the dates do not mature because of an exceptionally cool summer, or in regions where the summer heat is inadequate, they can be ripened artificially after being picked by exposing them to the sun during the hot part of the day spread out on blankets, and storing them indoors at night wrapped up in the blankets on which they have been exposed during the day. Mr. Hall Hanlon, near Yuma, Ariz. , often ripens considerable quantities of dates in this manner, which is that followed in northwestern Mexico (see p. 135). 30 THE BATE PALM. repacked in smaller boxes, holding from two-thirds of a pound to 10 pounds. (Fig. 5, p. 34, and PL X.) The methods above outlined apply to the Deglet Noor, which is the variety chiefly exported from Algeria and Tunis to Europe. Other varieties, such as the Rhars, which are full of sugary juice when ripe, are not so easily handled. The Arabs usually hang up the bunches and allow the juice to drain off into jars. This juice, which they call date honey, is preserved and used, and the fruit, when it has become somewhat dry, is then packed in boxes or more often in skins. Dates of this class are usually packed tightly, and may keep for many years without deteriorating. Somewhat the same style of packing is practiced at Bassorah and Maskat in Arabia, whence come most of the dates received in American markets. There the dates are packed tightly in layers in wooden boxes for export to America and Europe. The dates containing an abundance of sugary juice have the disadvantage of being sticky when unpacked, and are not suitable to serve as a dessert fruit. As before mentioned, the Deglet Noor does not have this drawback if properly handled. It has, however, the defect of drying rather rapidly, and from the very fact that it is not tightly packed in boxes it doubtless dries all the quicker. With reasonable care, however, it can be kept for some months in a cool, dry, well-ventilated storeroom, and probabty no other dried fruit having a value comparable to the Deglet Noor date can be put on the market with so little labor or at so little risk of loss. Practically the only hand labor required is that of arranging the dates in layers in the smaller boxes in which they are sent to the retail trade. TYPES OF DATES AND VARIETIES SUITABLE FOB CULTURE IN THE UNITED STATES. THE THREE TYPES OF DATES. Of the three principal types of dates cultivated by the Arabs, only one is exported to Europe and America. This comprises the dates, so familiar to us, called by the Arabs "soft dates." They contain some- times as much as 60 per cent of their weight of sugar, and are, in fact, candied on the tree, being preserved from decay by the enormous amount of sugar they contain. They contain more or less of a sirupy juice, which is in some varieties so abundant that it must be allowed to drain off before they can be packed. The second type comprises sorts very like those just mentioned, but having a much lower percentage of sugar — not enough to keep them from fermenting and turning sour. They do not dry readily and are usually eaten fresh from the tree as a table fruit, being more like grapes than like ordinary dates. The very early sorts are of this cate- gory and do not stand shipment to long distances, though they will prove of great value for home consumption and may be sold on the TYPES OF DATES. 31 local markets. The Wolf skill date (see fig. 3) from Winters, Cal., is one of these sorts, as is also the Amaree, the earliest date known in the western Sahara, which has been recently introduced into Arizona. The third category embraces what are known to the Arabs as " dry dates. - ' These are almost entirely unknown to Americans or Europeans, but are very much esteemed by the Arabs, who consider them to be better for every day consumption than the soft dates, which latter thev regard rather as a luxury than a staple food. These dry dates are not at all inclined to be soft or sticky when ripe, and are frequently so hard as to be difficult to eat. They are said to drop to the ground as they ripen, and are gathered by simply picking them up from beneath the palms as they fall. If stored in a dry place and protected from weevils, they may be kept for years without deteriorating. Dates of this type are as yet wholly unknown in our markets, but inasmuch as they are often of excellent flavor," and are cleaner, keep better, and are more easily gathered and packed, they can be sold cheaper than soft dates. It is not unlikely that the best sorts of dry dates may become favorably known and may be eaten in place of Deglet Noor dates as a dessert fruit, especially when the latter sort is out of sea- son; say, from April to October. . Mr. O. F. Cook suggests that dry dates may attain popularity as a result of the modern ten- dency toward the use of nuts, cereal preparations, and other foods Which do not require COOk- FIG 3._wolfskm dates grown at Winters, Cal. ing, since they would be prefera- ble to the sweeter soft dates as a regular article of diet, and could be had at any time of the year in prime condition. VARIETIES OF DATES SUITABLE FOR CULTURE IN THE UNITED STATES. When the writer made his last journey to the Sahara in order to secure offshoots for planting in the Cooperative Date Garden atTempe, in Arizona, and even when his first report b on the date palm was pub- «A palm which bears dry dates of excellent quality, though of rather small size, was imported by the Department of Agriculture in 1889, and has fruited for some years in the Salton Basin in southeastern California at Coachilla. This palm is probably a seedling and not an offshoot of a named variety as was at first supposed; it may be called the Coachilla date, and has fruits about H to 1 J inches long and five-eighths inch wide. They are brownish amber in color, much wrinkled, and have a dull meal bloom on the surface. The seed is small, light gray in color, blunt, and with a more or less evident furrow on the back. The flesh, though hard, is free from fiber and of very good flavor, with a persisting and agreeable aftertaste. &" The date palm and its culture," Yearbook of the Department of Agriculture, 1900; also reprinted and distributed separately. 32 THE DATE PALM. lished, it was doubtful whether the best late-ripening sorts of dates could succeed in any of the arid regions of the Southwest which had then been irrigated, and consequently particular attention was given to early-maturing sorts, sure to ripen fully in most parts of Arizona and California. Many early sorts have been secured by the writer from the Sahara, among them the Amaree, Tedmama, Areshtee, Hal- looa, Teddala, Timjooert, .Rhars, Tennessin, and Bent Keballa, and Mr. D. G. Fairchild has recently secured the Hayani, the earliest sort grown in lower Egypt. Several medium or early sorts already exist in California and Arizona — among others the Seewah, imported from Egypt by the Department of Agriculture some thirteen years ago, and a number of seedlings which have originated in this country, such as the very early Wolf skill (see fig. 3), the moderately early Lount No. 6, and the Bennet date (see fig. 4), which latter has a remarkably low proportion (1 to 11) of pit to flesh. With so many early and medium sorts to choose from, it is probable that some can be found capable of ripening all along the northern range of date culture in Texas, New Mexico, and Arizona, and throughout the interior valley region of California. The Rhars, in particular, is a promising variety for cooler climates, as the fruit ripens very early and is of good quality, while the plant is very vigorous and easily propagated by offshoots. Its principal drawback is that 'date,' from Phoe- the fruits are sticky, being so full of sirupy juice that nix, Ariz. j.ney are (Jif£cuit to cure, and must usually be packed closely in skins or boxes for shipment. It is not improbable, how- ever, that a good system of curing and packing would get rid of this sirup and leave the dates in a condition like that of the oriental dates commonly sold in America. A large number of the offshoots of the Rhars variety was obtained in 1900, part being sent to California and part to Arizona. The Rhars offshoots planted at Tempe in July, 1900, have made a remarkable showing; nearly 10 per cent of the plants (17 out of 176) flowered and bore a small crop of fruit only two years after being set out. ''The Rhars proved to be an exceedingly sweet, tender-skinned date, maturing in September and October, and can probably be grown in cooler localities than Salt River Valley."05 Professor Forbes writes that, u judging from preliminary experience, the Rhars seems to be a good commercial date, being very sweet, and drying in ten days to two weeks time to a firmness permitting of packing and shipping. « Forbes, R, H, Thirteenth Annual Report, Arizona Experiment Station, 1902, p. 243, TIIK 1)Kt>. shows that of the entire 38± plants set out in the Cooi»erativr Date Garden at Tempo and at Phoenix, 294 were living, while !»o wnv dead. ' These figures show that over 75 per cent of the offshoots have become established. (See Pis. XXI and XXII.) More than so per cent of those sent directly from the Sahara by the new system of packing- lived, but the average was reduced by the plants that had been grown in tubs a year before shipment, of which only about ;>s per cent lived. The offshoots simply packed in straw came through as well as those carefully wrapped about the base with moist moss or packed in char- coal. Inasmuch as only 70 to 75 per cent of the offshoots are expected to live in the Sahara when they are planted in the open without pro- tection, as was done at Tempe,6 the remarkable record was made of securing the growth of more offshoots in Arizona after a two months' voyage than would be expected to live in the Sahara, and that, too, even with the most inexpensive method of shipment that could be imagined — that of simply packing the suckers closely together in dry straw in ordinary wooden cases. This experiment has demonstrated the possibility of importing date offshoots from the Sahara and placing them in the deserts of the South- west in practically as good condition as when they were cut off the parent tree. The importance of this experiment is obvious, for it renders it certain that offshoots can be transported to great distances without loss, and makes it possible to undertake the culture of dates on a commercial scale by importing offshoots for planting. Doubtless means will be found to supply the demand for offshoots as soon as it arises b}r importation from the Sahara. In the meantime many of the best sorts of southern Algeria are on trial at Tempe, Ariz., and doubtless some will be found adapted to the climatic conditions there. As was previously noted in the paragraph on varieties, it is greatly to be desired that the Deglet Noor and other late sorts be set out as soon as possible in the Salton Basin, in order that there may be a prac- tical demonstration of the suitability of this region for the culture of the choicest sorts of dates. THE DATE PALM AS A SHELTER FOB OTHER FRUIT TREES. In many parts of the northern Sahara the date palm is almost as important as a shelter and partial shade for other fruit trees as it is for its own fruit. At the time of the Roman occupation of Africa these oases were largely planted to olive trees, some of which, indeed, still remain — giant stems perhaps 1,500 years old. It happens that the « Forbes, K. H. Thirteenth Annual Report, Arizona Experiment Station, 1902, p. 242. &Marcassin. L' agriculture dans le Sahara de Constantine. In Annalee de 1'Inst Agronomique, 1895, p. 62 of reprint. 44 THE DATE PALM. olive is about the only other fruit tree which is able to stand without injury the fierce heat, intense light, and the driving sand storms of the Sahara, and even the olive itself grows better and yields more fruit if planted under the protecting shelter of the date palm. Most other fruit trees, such as the apricot, peach, almond, pomegranate, fig, and jujube, can be grown successfully in the Sahara only in the shade of other trees, and do best where grown under the date palm. In the northernmost oases of the Sahara the dates are frequently of inferior quality, whereas the other fruit trees do better here than in the hotter and drier regions farther south. Many of these northern oases have veritable orchards growing under the half shade furnished by the crown of slender leaves of the date palms far above. This is well shown in Plate XII, which represents a fig orchard growing under date palms at Chetma, Algeria. It sometimes happens that vegetables are grown under the fruit trees, in which case it is possible to see three crops occupying the soil — first, the date palm, towering far above; then the fruit trees, and under them the more delicate and shade-loving garden vegetables. It is not at all impossible that in some parts of our own Southwest the date palm may prove very useful in the manner above described, serving as a shelter and partial shade to more delicate fruit trees which thrive perfectly in regions where the summers are far too cool to allow of the culture of the best sorts of dates. IRRIGATION OF THE DATE PALM. AMOUNT OF WATER NECESSARY FOR A DATE PALM. The date palm requires a continuous supply of moisture about the roots and can not maintain itself in as dry a soil as can some desert plants. Much experience has been accumulated by the French planters in the Algerian Sahara as to the amount of water necessaiy to enable a date palm to grow and fruit well. M. Jus, the celebrated civil engi- neer, who has done so much to reclaim the northern Sahara by a study of its artesian water supply, considers a that each palm tree requires one-third of a liter (0.35 quart) per minute at the flowing well or main irrigating canal, and palms which receive from 0.4 to 0.5 of a liter (0.42 to 0.53 quart) per minute are more vigorous and yield more fruit even if crops are grown underneath. If each tree receives 0.35 quart per minute this would amount to 126 gallons per day, or about 17 cubic feet. At 1 pint per minute the daily consumption would be 180 gallons, or a little more than 24 cubic feet. These data are not for the amount of water actually furnished the trees, but for the amount which must be allowed for each tree at the head of the principal irri- gating canals. Of course some of the water is lost by evaporation and seepage before it reaches the palms. a Jus, H. Les oasis de POued Rir', Paris (Challamel), 1884. AMOUNT OF WATER NECESSARY. 45 M. Holland, Avho has written a very complete account of the water supply of the Algerian Sahara," and who is himself one of the mem- bers of a firm which has created extensive date plantations in the Oued Rirh country, in the Algerian Sahara, considers that one-half liter (0.53 quart) per minute should be allowed to each palm to secure, the best results. M. le commandant Rose, himself an experienced planter, has pub- lished a most detailed statement6 regarding the practice of irriga- tion in the Oued Rirh country, where the water supply is furnished by artesian wells. He recommends 24 irrigations of 3 cubic meters (7i>2.r> gallons) each, making 72 cubic meters, or 19,021 gallons during the year. During the hot season, from June to September, inclusive, weekly irrigations are practiced, 17 in all, consuming 51 cubic meters, or 13,473 gallons per tree, which is at the rate of about 113 gallons per day, or about 0.314 quart (0.3 liter) per minute, the lowest of the three estimates. During the autumn and winter 2 irrigations, and during spring 5 irrigations, are prescribed. When the supply of water is invariable, as for example the flow from an artesian well, it is necessary to plant only the number of palms that can be properly irrigated by the available water supply during the hot season, when the amount needed is greatest. Where irrigation is practiced by means of water conducted from rivers or from storage reservoirs in canals, as is the case in most of the arid regions of the Southwest, it will be even more necessary to determine carefully how much water can be had in summer to avoid planting more dates than can be properly irrigated. In the plantations made recently by French proprietors in the Alge- rian Sahara, the date palms are usually set out 8 meters, or 26 feet, apart, making 143 to the hectare, or 60 to the acre. Some of the planters consider this distance too small and plant about 10 meters (33 feet) apart, making about 40 to the acre, while others, among them the celebrated civil engineer Rolland, consider 200 to the hectare, or about 80 to the acre, as being the best number to plant. Taking 60 to the acre, 26f feet apart, as a good number to plant, the amount of water needed per acre can easily be calculated. Using Rose's estimate of 19,021 gallons per tree per annum, 3£ acre-feet of water would be required, of which 2-f acre-feet would be used during the four summer months from June to September, inclusive. Using Jus's estimate, which puts the least amount necessary at one-third « Rolland, Georges. Hydrologie du Sahara algerien (chemin de fer transsaharien ) , Paris, Imprimerie Rationale, 1894, p. 9. & "La culture du dattier dans le sud constantinois, par un homme du sud." Alger. 1898, Pierre Fontana & Cie, Paris, Augustin Challamel. 8°. 20 pp. The identity of the author of this pamphlet was disclosed by Eolland (Hydrologie du Sahara algerien, p. 167). 46 THE DATE PALM. liter (0.35 quart) per minute, or 126 gallons per day, a trifle over 4 acre-feet would be required, of which nearly 3 acre-feet would be used in the four hottest months, from June to September, inclusive. On the basis of Holland's estimate, which is also given by Jus as the optimum quantity, viz, one-half liter (0.53 quart) per minute, or 190 gallons per da}-, some 5i acre-feet a year would be required, of which 4 acre-feet would be used during the four summer months, or at the rate of 16 acre-feet per annum. The amount of water needed per acre depends of course directly on the number of date palms per acre, and in planting care should be taken not to set out more than can be irrigated with the water supply covering the land. It must be remembered that the figures given above are for the western Sahara, a region noted for its extreme dryness, where the evaporation from a free surface of water often averages nearly one- half inch per day during the three summer months — June, July, and August. It is probable that a smaller amount of water would suffice in regions where the air is not so dry and consequently where the evaporation is less, as, for example, in the Salt River Valley and most other parts of southern Arizona/ while in hotter, drier regions, such as the Sal ton Basin, even more will be required. In the latter region it will be well to allow only about 12 palms to each acre-foot of water available, and this only if the water can be had whenever desired during the summer. This would permit planting some 50 date palms to the acre where 4 acre-feet of water are available whenever needed during the year. It must be remembered in considering the needs of the date palm that the water supply must be practically continuous; that is to sa}^ that the ground must in some way be kept damp throughout the entire year. It is probable, however, that the date palm does not require as much water as do ordinary fruit trees. It is, indeed, probable that owing to their having thick, leathery leaves, protected by a coating of wax, they evaporate a considerably less quantity than would an ordi- nary fruit tree having delicate leaves not adapted to withstand the hot, dry air of deserts. It is nevertheless necessary for the roots to have o At Tucson, Ariz., the average of three years' records taken at the University gives the annual evaporation from a free surface of water at 77.7 inches, and the average rate during the three hottest months, June, July, and August, at one-third inch per day. At Tempe, in the Salt River Valley, Arizona, a calculation by the United States Geological Survey from imperfect data gives 91 inches as the probable annual evapo- ration. At Biskra the careful records of M. Colombo show a mean annual evapora- tion during the ten years from 1884 to 1893 of 2.8374 meters, or 111.7 inches, averaging 12.47 mm., or 0.4915 inch (very nearly one-half inch) per day during June, July, and August. In the Oued Rirh country, where most of the observations relative to the amount of water necessary for irrigating date palms have been made, the rainfall is less than at Biskra and the temperature higher, so the evaporation is doubtless greater. AMOUNT OF WATER NECESSARY. 47 access to moist earth throughout the entire year, since, as has hern stated above, the date palm is not at all a desert plant, in the sense of being able to exist on very dry soil, and would die in many <>f the situ- tions in the Southwest where cacti and yuccas thrive. Where the supply of irrigation water is limited, as at IViskra. where there is only 0.12 liter per minute available for each palm and where the soil is very heavy and consequently difficult to saturate, irrigation is commonly practiced by filling up with water a cavity — "dahir" excavated at the base of the tree (PL XVII, fig. 2, and Yearbook, 1000, PI. LV, fig. 3). Where water is more abundant and especially where crops are grown under the palms it is customary to flood the whole surface of the ground, the land being divided into small beds from 10 to 30 feet in diameter, which are surrounded by a slightly raised rim (PI. XVII, fig. 1). When irrigated the whole bed is flooded, the water being retained by the surrounding ridge. A larger amount of water is required when applied in this manner than would be necessary if poured into a trench at the side of the palm, but the alkali is washed into the subsoil by surface flooding, whereas it is brought to the sur- face by the trench system, which should never be followed in danger- ously alkaline soils. In the Salton Basin in particular, where the subsoil is often heavily charged with alkali, the land should always be watered by flooding or else by deep furrows, even where the surface soil does not contain harmful quantities of alkali." Where there is water at a short distance from the surface within reach of the roots, as is the case in the area about the Cooperative Date Garden at Tempe, Ariz, (see Pis. XXI and XXII), at Farfar, Algeria, in the western Zab, between Fougala and Biskra, Algeria (PI. XIV, fig. 1, and Yearbook, 1900, PL LIX, fig. 7), and in the Souf country in the Sahara (fig. 8, p. 69) the amount of water required for irriga- tion is less when once the palms have become established. They can even exist without any irrigation whatever from the surface, although in this event they do not grow as well and bear very much less fruit, probably because of imperfect aeration of the soil about the roots and because of the continual rise of alkali from the subsoil, as will be explained in the chapter on drainage. Well aerated running water is desirable for date palms and water- logging of the soil must be prevented. If these conditions are fulfilled this plant can live and thrive when irrigated with water so salty a> to kill all ordinary plants, as will be shown later in treating of the alkali resistance of the date palm. «Snow, Hilgard, and Shaw (in Bui. 140, Cal. Exp. Sta., pp. 36-39) recommend for the Salton Basin first washing the alkali down by surface flooding and then pre- venting its subsequent rise by deep-furrow irrigation. However, the date palm is not sensitive to surface accumulation of alkali when once established, as will l>c shown farther on (see p. 117). 48 THE DATE PALM. Irrigation by menus of flooding is sometimes practiced in Egypt for the date palm, as has been done for all sorts of crops since remote antiquity. The water covers the land to a depth ranging from a few inches to several feet (see PI. XI), and remains on the soil for about six weeks. a This method of irrigation is riot likely to prove desirable anywhere in this country unless it be in the flood-plain of the Colorado River in California and Arizona (see p. 131). It may be desirable to use this method of flooding in order to wash the alkali out of the sur- face layer of the soil where the accumulation of alkali in the upper layers of the soil is so great as to prevent the best growth of the date palm. It is of interest in this connection to note that the Egyptian date palms are able to endure having their roots submerged for long periods without appreciable in j ury . Mr. D. G. Fairchild has described a very interesting system of com- bined irrigation and drainage practiced in the date plantations along the Shat-el-Arab River at the head of the Persian Gulf, which are doubtless the most extensive in the world. The level valley land along the river is cut up into small rectangles, 10 to 15 by 20 to 30 feet on a side, by irrigation ditches, through which, twice a day, water flows when the river is backed up by the tide. As the tide recedes the water flows out of the ditches, preventing stagnation and caus- ing a lowering of the water level in the soil. The soil is doubtless thoroughly aerated by this alternate rise and fall of the level of the ground water. By this interesting system of tidal irrigation, which, without any trouble beyond the first labor of digging the ditches pro- vides for very perfect watering, drainage, and aeration of the soil, date palms thrive in this region where the soil is as pure an adobe as the clay of a brickyard.6 Such a system of combined irrigation and drainage can, of course, be applied only where a river is backed up by high tides. No such con- ditions occur, or at least not on any considerable scale, within the date regions of the United States, since the region along the Sacramento River in California where tidal irrigation can be practiced is so cooled in summer by the cold winds and fogs from the Pacific that none but the very earliest sorts of dates could mature. Along the Colorado River, near its mouth in Mexico, it is possible that tidal irrigation could be used in date culture, since the tides in the Gulf of California are very high and the climate and soil in this region are favorable to the culture of early and midseason dates/ a Kearney, Thos. H., and Means, Thos. H. Crops used in the reclamation of alkali lands in Egypt, Yearbook, Department of Agriculture, 1902, p. 504. & Fairchild, D. G. Persian Gulf Dates and Their Introduction into America. Bui. No. 54, Bureau of Plant Industry, U. S. Department of Agriculture, 1903, p. 14. c However, the head of tide water is only about fifteen miles above the mouth of the river (as may be seen on fig. 10, p. 102), and consequently there is not room for such immense date plantations as those described by Fairchild around Bassorah. WARM IRRIGATION WATER ADVANTAGEOUS. 49 In many parts of California and possibly in some parts of Arizona there is enough rainfall to support the date palm without irrigation (see p. 124). The Wolfskill date palm at Winters, Cal., for example, is never irrigated, yet bears abundant crops of good dates every year. In regions where the winters are very cold it is unwise to irrigate late in summer, except when necessary to keep the palms alive, since abundant watering forces a tender new growth, which is likely to be killed by the freezes of the succeeding winter. At Tulare, in the San Joaquin Valley, California, where there are from 6 to 34 severe frosts every winter and where the temperature sometimes falls as low as 17° F. or lower, the gardeners of the substation of the Agricultural Experiment Station consider it unwise to irrigate date palms after the month of June. WARM IRRIGATION WATER ADVANTAGEOUS. The growth of the date palm and the maturing of its fruit are hastened by supplying warm water to the roots. For example, in the oasis of Chetma, Algeria (see PL XII and Yearbook, 1900, PL LIX, fig. 8), largely supplied with water from warm springs having a temperature of 94.1° F. (34.5° C.), the Deglet Noor date ripens early in the season, especially on those trees growing near the springs and which, consequently, receive warm water even in winter and early spring, when the air is still cold. Biskra, near by and at nearly the same level, though less protected against cold winds, is also irrigated largely from springs, but the temperature of the water of these springs is only 70° to 81° F. (21.5° to 27.33° C.), and the water is cooled in winter and spring by admixture with the run-off from the Atlas Mountains to the north and by flowing a couple of miles in open canals before it reaches the nearest date palms. Here the Deglet Noor date does not mature so well as at Chetma and is not of the best quality. The artesian wells of the Oued Rirh country (see map, PL II, p. 76) furnish water of a temperature ranging from 76.3° to 79° F. (24.6° to 26.1° C.), and in the Souf country the ground water to which the palms send down their roots is much colder, having a temperature of only 57.2° to 68° F. (14° to 20° C.); but in these regions the summer heat is much greater than at Biskra and usually suffices to enable the Deglet Noor to mature perfectly. In the Salt River Valley, Arizona, the irrigation water is conveyed in open canals mostly shaded by cottonwood trees. The temperature of the water naturally varies with the season. In June, when the tem- perature of the air ranged from 82° to 104° F., Professor McClatchie found the temperature to range from 73° to 94° F. in the canals and from 82° to 88° F. in the smaller irrigating ditches. It should be noted that in June the supply of irrigating water is less than for any other month of the year, and probably in February, March, and April, 13529— No. 53—04 4 50 THE DATE PALM. when the canals are full of the water from melting1 snows on the sur- rounding mountains, the temperature would be much lower. The Salton Basin is supplied with water diverted from the Colorado River near Yuma and conducted some 40 to 60 miles in open ditches before it is put on the land. The annual overflow of the Colorado River occurs in early summer, usually in June or July, and is caused by the melting of the snows on the Rocky Mountains in Colorado, Utah, and Wyoming. This cold water fortunately reaches the Colo- rado Desert at a time when the heat is great, so that in flowing in the large open canals and in the shallow laterals and in soaking through the hot surface layers of the' soil it will undoubtedly be warmed con- siderably before it reaches the roots of the date palms. On the whole the conditions are exceptionally good in the Salton Basin, for the most abundant supply of water occurs in early summer or midsummer, just when the plants have greatest need for it. The annual overflow of cold waters from the melting snows is doubt- less the principal cause of the failure of the date palms to mature their fruit properly on Mr. Hall Hanlon's place in the Colorado River flood plain in California, near Yuma, Ariz, (see PI. XX, fig. 2). The tempera- ture of the soil and of the air in this overflowed area and in adjoining areas at nearly the same level is doubtless much lower than at the town of Yuma, for instance." Even at Yuma the summer heat is less than at Phoenix and very much ICGG than in the Salton Basin. It is clear then that no conclusion unfavorable to the culture of dates in the Salton Basin can be drawn from the failure of these palms in the flood plain to mature their fruit. Early varieties, such as the Rhars and Teddala, will probably ripen even on these overflowed lands (see p. 132). DRAINAGE FOB THE DATE PALM. Although the date palm can withstand very much more alkali than any other crop plant, it does not endure having the soil about the roots water-soaked. Good drainage is as essential for it as for any other fruit tree if good crops are to be expected, and, unless the soil drains naturally, the superfluous water must be removed, usually -by means of open ditches or with tile drains. Proper aeration of the soil about the roots is essential to enable the date palm to grow well and yield abundantly (see p. 80). Good drainage also permits the alkali to be washed out of the soil by means of heavy irrigation, and, doubtless, this also favors the growth of tho palms. It is, however, worthy of being noted that the excessively alkaline water which flows off in the drainage ditches is used in some parts of the Sahara to irrigate date palms which occupy land lying at a lower level. Such palms, though « According to Mr. Bernard G. Johnson, of Mecca, CaL, there is a drainage of cold air from the hills toward Mr. Hanlon's date plantation which renders it one of the coldest sites in the vicinity of Yuma. DRAINAGE. 51 less vigorous than those receiving good water, nevertheless produce moderate crops of fruit (see p. 98). In most date plantations made by the French in the Sahara, drainage is provided by means of open ditches from 2 to 6 feet deep, running between alternate rows of palms, or at distances of about 50 feet apart (see PL XVII, tig. 1). Very unusual conditions of drainage are found at the oasis Fougala, Algeria (see PL XV, fig. 1), as will be explained in treating of the alkali soils collected at that place (pp. 78 and 84). The superfluous water there runs off through holes in an impervious hardpan, and the downward flow of water through the holes, induced by surface irrigation, has washed the alkali out of the surface soil, has aerated the subsoil, and has had marvelous effects in promoting the growth and increasing the yield of the date palms, which had managed to live for years before surface irrigation was begun with the supply of water absorbed by the roots from below the hardpan layer. It will doubtless be found necessary to irrigate date palms about Tempe, Ariz.9 even where their roots penetrate to the subsoil con- stantly wetted by the water that seeps down from the irrigated fields located at higher levels. Unless this is done the palms are likely to become stunted and sterile, as they were at Fougala before surface irrigation by artesian water was commenced. The presence of a hardpan layer, as at Fougala, may be advanta- geous in providing a means of drainage through holes made under each tree, while at the same time confining the drainage water below the hardpan, thereby preventing its rising to the surface by capillarity and carrying with it the alkali of the subsoil. When no hardpan exists, as at Tempe, a certain amount of drainage can nevertheless be accomplished, since the water applied at the surface drains into the great body of ground water, which has a practically constant level unless raised by excessive irrigation. In case the subsoil is too impervious to permit quick seepage from the surface to the ground water, outlets for drainage water can sometimes be provided advan- tageously by putting down wells. In most parts of the Salt River Valley the natural drainage is good and no ditches or tile will be needed. In the Salton Basin drainage is impeded by the impervious nature of the clay, which occurs in many places as surface soil and nearly everywhere as subsoil. Drainage is especially desirable here, for the subsoil is often laden with alkali even where the surface soil is free from harmful quantities of salts. Natural drainage, nevertheless, will probably suffice for the date palm in many parts of this region, provided the level of the ground water is not raised too high by excessive and ill-timed irrigation. In some places, where natural drainage is insufficient, occasional open ditches will provide adequate drainage, especially where the soil is a sandy 52 THE DATE PALM. loam or a loam. The lands lying near the New River or Salton River beds, or near Mesquite or Salton Lake, can be drained into these lower levels, and in many other places wells may be put down to pro- vide an outlet of drainage water into the great body, of ground water which lie$ from 20 to 50 feet below the surface. Though required for the best growth and successful fruiting of the date palm, drainage is less necessary than for most other trees. Even if the ground water of the Salton Basin rose to within reach of the roots it would not kill the date palm, for, although this ground water is very brackish, con- taining from 0.4 to 0.6 per cent of dissolved salts, and would kill most ordinary plants, it is less alkaline than some of the artesian water used to irrigate flourishing date plantations in the Oued Rirh country in the Sahara (see pp. 86 and 121). EFFECTS OF ATMOSPHERIC HUMIDITY AND BAIN ON THE DATE PALM. An essential requirement of the date palm, in order that it may pro- duce fruit of the best quality, is that the air be very dry during the season when the fruit is developing. Regions having abundant sum- mer rains, and even those having a heavy precipitation in autumn, are unsuited to the profitable culture of this tree, but rains in winter ma}^ be beneficial. It has usually been held that the presence of humidity in the air is directly disadvantageous, but it is probable that the chief action of water vapor in the atmosphere is indirect and results from its peculiar action in screening out the heat from the sun's raysf/ and thereby preventing the temperature from going to the excessively high degree necessary to ripen the fruit properly. The same dry air which allows excessive heating during the day permits an equally great fall of temperature by radiation into a cloudless sky at night and brings about the enormous daily range of temperature characteristic of desert regions. The date palm, however, suffers no check from cool nights, unless the temperature falls below a point somewhere about 18° C. (64.4° F.), and is favored by excessively high temper- atures, which are, indeed, necessary for the production of dates of the highest quality. Table 1, on the following page, gives the mean relative humidity at four points where the date palm is grown, for the months of April to September, inclusive. « Very, Frank W. Atmospheric Radiation. Bui. G, Weather Bureau, U. S. Dept. of Agriculture, 1900. EFFECTS OF HUMIDITY AND BAIN. 53 TABLE 1. — Humidity of the air at four desert stations where dates are grown. Mean rela- tive hu- Mean rela- Locality. Altitude. midity of six months, tive hu- midity of Remarks. Apr. 1 to Sept. 30. month. Feet. Per cent. Per cent. frharda'ia, Algeria BNkra \lgeria 1,804 449 1,068 23 30 33 14 (July) 25 (June) 24 (June) Dates are of excellent quality. > Dates are largely grown, but are not of the best quality. - Dates of the earlier 'sorts ripen well. » Phoenix Ariz Tucson Ariz .... 2,432 35 19. 9 (June) Dates ripen imperfectly here, pro- bably because of deficient sum- mer heat at this altitude; pos- sibly also because of too great humidity. 4 1 Records of Dr. Amat for the years 1883, 1888, and 1889. 2Schirmer, Sahara, p. 64. 3 Records of Weather Bureau Station, completed by A. J. McClatchie, Bui. 37, Ariz. Agr. Ex. Sta., p. 209, average of five years' record. 4Boggs and Barnes,* Bui. 27, Ariz. Agr. Ex. Sta., p. 37, record for the years 1892-1894. The mean for October is 36,3 per cent. The following averages show the amount of atmospheric humidit}7 at Phoenix and Tucson, Ariz., for each month from the flowering to the ripening of the fruit of the date palm, and a partial record from GhardaTa, Algeria: TABLE 2. — Mean relative humidity at desert stations during date season. Average, Locality. Length of record. April. May. June. July. Aug. Sept. Oct. Nov. April to Novem- ber. Phoenix 5 years 33 0 26 0 24 0 37 0 40 0 39 0 40 0 43 0 35 25 Tucson 3 vears 28.1 25.5 19.9 42.8 51.8 39.6 36 3 40 2 35 52 Ghardai'a 1 vear (1883) 28 1 37 5 32 3 11 9 14 4 22 1 Do 3 years 23.0 14.0 19.0 The occurrence of a well-defined rainy season in July and August in southern Arizona causes the humidity for those months to be much higher than it is in the Sahara, where all three summer months are very dry. The following table showing the average rainfall for each month at Biskra and Ayata in the Sahara, at Phoenix and Yuma, Ariz., and at Salton, in the Salton Basin, California, brings out this difference in climate: TABLE 3. — Mean monthly rainfall, in inches, at Biskra, Ayata, Phoenix, Ynma, and Salton. Locality. Jan. Feb. Mar. Apr. May. June. July. Aug. Sept. Oct. Nov. Dec. Year. Bi «kra, Algeria 1 .... Ayata. Algeria2 0.52 .08 57 0.64 .27 89 1.38 1.06 68 0.94 1.06 30 0.83 .16 16 0.33 0 07 0.25 0 85 0.26 0 97 0.57 .04 54 0.64 .12 62 0.93 1.21 44 2.17 .53 1 12 9.46 4.53 7 21 Yuma, Ariz Salton, Cal.4 .40 .43 .54 .62 .24 .21 .07 T. .04 .07 T. T. .14 .19 .37 .14 .14 .13 .30 .12 .28 .12 .53 .56 8. OR 2.56 1 Records of M. Colombo, published by Marcassin in Annales de 1'Inst. Nat. Agronom., 1895, 10 years. •-'Records of M. Cornu, read from charts exhibited at Paris Exposition. 1900. 4 years. ^Records of the Weather Bureau, compiled by Thos. H. Means, Second Rep., Div. of Soils, U. 8. Department of Agriculture, 1900, p. 292. * Records of the Weather Bureau, compiled by Prof. Alexander G. McAdie, California Climate and Crop Service, April, 1901, 12 years. 54 THE DATE PALM. During- July and August more than three times as much rain falls at Phoenix as at Biskra, although the annual rainfull is nearly one-third greater at the latter station. Unfortunately records are not available for the Salton Basin, but the very low rainfall in spring, summer, and autumn, and the exces- sively high temperatures which prevail there render it certain that the humidity is very slight — probably somewhat lower than at Gharclai'a. There is, however, as in Arizona, a well-defined rainy reason in July and August, which tends to raise the humidity for those months. RAINY WEATHER DISASTROUS TO THE FLOWERS AND RIPENING FRUITS OF THE DATE PALM. Besides its indirect harmful action in decreasing the amount of sun- shine and heat and in increasing the amount of humidity in the air, cloudy or rainy weather is directly injurious to the date in preventing the fertilization of the flowers in spring, and also in bringing about the decay or dropping of the fruit when it is ripening in autumn. When the flowers are being pollinated a spell of wet, cloudy weather, by spoiling the pollen may hinder the setting of the fruit, though usually the harm can be remedied by repollinating with a fresh spray of male flowers when the weather becomes dry. In autumn the effects of rainy, humid weather are much more disastrous and may entail the loss of the entire crop by causing the dates to ferment and spoil just when they are ripening. No misfortune is more feared by the date growers in the Sahara than wet weather at this time. Most varieties of date palms flower in April and May in Arizona, as in the Algerian Sahara, and the best sorts begin to ripen in October and November. The following table shows the amount of rain for the months of April and Ma}r, in spring, and October and November, in autumn, for a number of points in the Southwest, and also for Biskra and Ayata in the Sahara. RAINY WEATHER DISASTROUS. 55 TABLE 4.—Arerage, highest, mid lowest rainfall, in inches, at flowering and ripening seasons of the date palm at stations suitable for date culture. Locality. Alti- tude. Rainfall during flowering season. April. May. Mean. Maxi- mum. Mini- mum. Mean. Maxi mum. Mini- mum. Phoenix, Ariz. (Salt River Vallev) 1. . . Feet. 1,068 900 1,110 1,200 1,244 Indies. 0.31 Tr. 0 .09 Tr. Inches. 1.25 Inches. 0 Inches. 0.16 .09 Inches. 1 Inches. 0 Buckeve (Salt River Vallev)2 Experiment Farm (Salt River Valley) 2 Peoria (Salt River Valley) 2 0 .18 Mesa (Salt River Valley) 2 o Average for five stations in Salt River Valley .08 .086 Maricopa.Ariz. (Upper Gila Valley) Casa Grande (Upper Gila Valley) l i 1, 1, 1 173 39S 553 .13 .11 .37 .75 .73 1.55 0 0 0 0 0 .10 .07 .18 .64 .34 .97 0 0 0 Florence (Upper Gila Valley) J Tucson, Ariz.1 2 430 141 .16 .07 .62 .55 .18 .04 1.09 .44 0 0 0 Yuma, Ariz.1 Mammoth Tank, Cal. (Salton Basin) * Salton, Cal. (Salton Basin)3 257 -263 .06 Tr. .80 .01 0 0 .02 .07 .30 .70 2756" Biskra, Sahara4 449 .94 3.03 .08 .83 ToT 0 Ayata, Sahara (Oued Rirh) 5 100 1.06 2.24 0 .16 .47 Locality. Rainfall during ripening season of late dates. Rainfall during year. Length of record. . October. November. Mean. Max. Min. Mean. Max. Min. Mean. Max. Min. Phoenix, Ariz. (Salt River Valley) ». Buckeye (Salt River Valley) 2 In. 0.50 .63 In. 2.80 In. 0 In. 0.44 .42 In. 1.66 In. 0 In. 7.08 6.60 In. 12.83 In. 3.77 years. 15 Experiment Farm (Salt River Val- ley) - .34 .48 7.01 Peoria (Salt River Valley) 2 .92 40 8.41 5.52 Mesa (Salt River Valley) 2 .31 .46 Average for five stations in Salt River Valley .54 .44 6.94 Maricopa, Ariz. (Upper Gila Valley) l Casa Grande (Upper Gila Valley) l. . Florence (Upper Gila Valley) 1 .28 .32 .63 1.51 1.81 1.80 000 .29 .33 .55 1.13 2.00 2.36 0 0 0 5.50 5.29 9.78 11.96 10.70 13.80 .88 1.73 5.35 18 14 13 Tucson Ariz * .53 .30 2.24 1.70 0 0 .48 .28 2.06 2.43 0 0 11.63 3.05 18.37 5.86 5. 26 .74 19 19 Yuma, Ariz. l Mammoth Tank, Cal. (Salton Basin)' Salton, Cal. (Salton Basin) 3 .12 .12 .68 .93 0 0 .14 .12 .73 .71 0 0 1.81 2.56 5.48 11.19 16.30 Tr. Tr. 23 12 Biskra, Sahara4 .64 1.73 0 ~93 1.97 .12 9.46 4.89 5.67 10 Ayata, Sahara (Oued Rirh) 5 .12 .28 0 1.21 2.05 .02 9.32 2. 52 «4 and 7 1 Records compiled by Boggs and Barnes, Bui. 27, Arizona Experiment Station. Table XVI. '-Records compiled by Thos. H. Means, Field Operations Divison of Soils, U. S. Department of Agriculture, Second Report, 1900, p. 292. 3Reeords compiled by Alexander G. McAdie, Cal. Sec., Climate and Crop Service, Weather Bureau, February, 1901, p. 4. •'Records of Colombo, published by Marcassin, L' Agriculture dans le Sahara de Constantine, in Annales de I'lnstilut National Agronomiqoe, 1895, p. 17 of reprint. 5Records of Cornu tor years ls%-ls<«), rend from charts exhibited at Paris Exposition. 1900. 6 Annual rainfall for 1889 to 1891, from Rolland, Hydrologie du Sahara nlgericn, p. ll.~>, is included 11 this table, making seven years in all. These records show that the Salt River Valley, the upper Gila Val- ley, Yuma, and even Tucson, Ariz., have less rainfall at the critical periods for the date palm than occurs at Biskra, Algeria, where date culture is the principal industry. Yuma, in the Colorado River 56 THE DATE PALM. Valley, in extreme southwestern Arizona, and especially Salton and Mammoth Tank, in the Salton Basin, in southeastern California, show decidedly less rainfall than occurs at Ayata, in the Oued Rirh country in the Sahara, where date culture is almost the sole industry and where the Deglet Noor variety is grown successfully. Even the maxi- mum rainfall in exceptionally wet years in the Salton Basin does not equal a the average rainfall for these critical months at Biskra. The number of rainy days, which is a matter of considerable import- ance in determining the suitabilit}^ of climate to date culture, runs closely parallel to the amount of precipitation, as may be seen by com- paring the following records for Biskra and Tucson with those given above for the rainfall: TABLE 5. — Number of rainy days at desert stations (Biskra, Algeria, and Tucson, Ariz.) during flowering and ripening seasons of the date palm. M Flowering season. Ripening season. £ 0 o> . April. May. October. November. Locality. 1 O> >> a a a | a d a 3 a I a a a d a a c I a j a a 2 j 1 B cS 1 1 1 i 1 1 |. i 1 5 Biskra, Algieria.. 449 10 3.4 7 i 3.5 6 i 2.6 5 0 8.6 7 1 Tucson, Ariz 2,432 5 .2 1 0 1.2 3 0 4.8 9 0 .2 6 0 The ideal climate for the date palm would be one that was rainless during the critical months. It is a matter of some interest to see how often this condition has been recorded for the Salton Basin stations. Rainfall records are available for twelve years (1889-1900) for Salton in the lowest part of the Salton Basin (263 feet below the sea level), and they show that the critical months were frequently rainless; at Mammoth Tank, in the eastern border of the Salton Basin (altitude 257 feet above sea level), the record for twenty-three years, from 1878 to 1900, is still more favorable, as is shown by the following table: TABLE 6. — Number of years in which no rain (or trace only) fell at Salton and at Mam- moth Tank, in the Salton Basin, California, during the months named. Month. Salton (263 feet be- low sea level). Mammoth Tank (257 feet above sea level). Number of years rainless. Total number of years recorded. Number of years rainless. Total number of years recorded. April... 11 10 9 8 8 7 12 12 12 12 12 12 14 20 13 12 13 7 23 23 23 23 23 23 May April and May ... . . . October November October and November . . « Except for one year of the twelve recorded at Salton, the rainfall in October, 1896, was 0.93 inch, exceeding the average at Biskra (0.64 inch), though not being more than half the maximum rainfall for the month ( 1.73 inches) at the latter station. RAINY WEATHER DISASTROUS. 57 At Salton, out of the twelve years recorded, only one had more than one-tenth of an inch of rain during the two months of the flowering season (April and May) and only two had over 0.28 inch rainfall during the ripening season. At Mammoth Tank, out of these twenty-three years, only one had more than three-tenths of an inch rainfall during the flowering season (April and May) and only three showed over three-tenths of an inch precipitation during October and November. At Biskra, in the Algerian Sahara, the rainfall records are available for the ten years from 1884 to 1893. During this period only one month during the critical periods was rainless, viz, October, 1893. Only once during the flowering period (April and May) was there as low as 0.39 inch rainfall, and only once during the season when the fruit ripens (October and November) was there as low as 0.31 inch of rain. At Ayata, some 100 miles south of Biskra, in the Oued Rirh country, where a specialt}r is made of the culture of choice Deglet Noor dates for the export trade, the rainfall for 1889 was 2.52 inches; for 1890 it was 9.32 inches; for 1891,a4.16 inches; for 1896, 7.60 inches; for 1897, 4.84 inches; for 1898, 2.79 inches, and for 1899,6 2.91 inches, an aver- age of 4.89 inches. The distribution of the rainfall at Biskra and Ayata, by seasons, in comparison with the average at Yuma in the Colorado River Valley and Salton and Mammoth Tank in the Salton Basin, is given herewith: TABLE 7. — Table showing seasonal and annual rainfall at stations in desert regions. Locality. Length of record. Winter rainfall. Spring rainfall. Summer rainfall. Autumn rainfall. Annual rainfall. Biskra Algeria (Sahara) Years. 10 Inches. 3 32 Inches. 3.16 I in-lit*. O.H4 fneka, 2. 13 Inches. 9.45 Ayata Algeria (Sahara) 7 1.81 1.49 ".09 1.50 4.89 Yuma, Ariz. (Colorado River Valley) Salton Cal (Salton Basin) 19 12 1.47 1.59 .35 .28 .51 .33 .72 .37 3.05 2.56 Mammoth Tank, Cal. (Salton Basin) 23 .93 .27 .29 .32 1.81 a During the years 1896 to 1899 almost no rain fell in summer. April, May, September, and October are sometimes rainless. It is noticeable that the summer rainfall is considerably higher at Yuma and at the Salton Basin stations than at Ayata, but that the spring and autumn precipitation is much less, rendering the climate decidedly more favorable for date culture. It is clear from the above tables that there is less danger from rain to date flowers or to the ripening fruits in the Arizona deserts or in the Salton Basin in California than at Biskra in the Algerian Sahara, where date culture is an established and profitable industry. Indeed, « Holland. Hydrologie du Sahara, p. 416. For the years 1889 to 1891, inclusive. & Records of Cornu exhibited at Paris Exposition, 1900. Amounts read from curves of charts for the years 1896-1899. 60 THE DATE PALM. than on the tops of old palms far above the surface. Old and vigor- ous trees might perhaps occasionally weather cold snaps where the temperature fell below 10° F., provided such were exceptional and occurred only at intervals of many 3^ears. In practice, then, four dif- ferent limits below which palms would be injured by cold might be set: (1) Young palms in active growth would be liable to injury if the temperature fell several degrees below freezing; (2) 37oung plants not in active growth and old palms if nearly dormant would be severely injured only by temperatures falling below 15° F. ; (3) old and dor- mant trees would be severely injured only by temperatures below 12° F. ; (4) most date palms would be killed and all would be seriously injured by the temperature falling below 10° F. , and date culture would be impossible in regions where such temperatures occurred more than once in a decade. These considerations show that the date palm has about as much resistance to cold as the fig tree, for example, with this impor- tant difference — that a fig tree is able to recover and grow again the next year, even if it be frozen to the ground by severe cold in winter. With the date palm this is not possible, since, if the growing bud of an old tree be killed, it is impossible for the trunk to sprout out again. In the Salt River -Valley, Arizona, the temperature not infrequently falls to 25° or 22° F., and at rare intervals goes as low as 12° or 13° F., which temperatures of course injure the date palm but have not killed any of the many fine trees growing in the valley, though young offshoots recently transplanted have been frozen to death a. No temperatures low enough to injure seriously even young date palms (below 18° F.) are recorded from any of the stations in the Sal- ton Basing and if the first winter after the plants are set out is passed safely no further danger from cold need be feared. a Even young palms seem more resistant to cold than has been supposed, for the severe cold of the winter of 1901-2, when a temperature of about 13° F., was reached, killed very few of the Saharan date palms in the cooperative garden at Tempe, which were planted in July, 1900. A few of the offshoots set out in 1901 passed through the cold weather without being killed, thanks probably to the protection afforded by wrapping them in several thicknesses of burlap sacking. It is now very clear that large offshoots withstand cold much better than small ones and besides bear the long voyage better. &The lowest temperature recorded at Salton is 20° F., with 22° F. at Mammoth Tank, where only 9 out of the 23 years recorded show temperatures below 30° F. At Indio in the northern and at Imperial in the southern part of the basin temper- atures of 18° F. are recorded. At Indio the temperatures are probably lowered by cold winds which blow down from the mountains to the north and west through a valley-like prolongation of the desert to the northwest. The young date palms which grow about Indio without any protection are proof that the winters are not too severe even for very young plants. However, winter cold is the greatest danger to which the date palm is exposed in the Salton Basin, and intending planters should be careful to avoid low, cold situations in setting out date palms, for Snow reports on January 2, 1902, at 8 o'clock a. m., a temperature of 13° F. and ice 2 inches thick. (Bui. 140, Cal. Exp. Sta., p. 45.) A. V. Stubenrauch states that this record is for Imperial, Cal. LATE FROSTS AND DRAINAGE OF COLD AIR. 61 THE DATE PALM FLOWERS LATE IN SPRING AND ESCAPES INJURY BY LATE FROSTS. A very great advantage of the date palm is that it flowers late in spring, after all danger of frost is over," whereas many other fmit trees, among them the peach, the apricot, and especially the almond, bloom very early and are exposed to much risk of having the flowers or }Toung fruits killed by late frosts. The records available from the Sahara are very poorly calculated to show how much cold the date palm can stand, for the whole northern and western Sahara is characterized by very warm winters. Tempera- tures of — 5 to — 7° C (21.4° to 23° F.)are recorded from date oases in the Sahara, but the date palm is able to endure lower temperatures than these without serious harm resulting. The northern limit and the limit in altitude in northwestern Africa at which dates can be grown are set more by the deficient summer heat failing to ripen the fruit than by the cold in winter.6 DRAINAGE OF COLD AIR AND INVERSION OF TEMPERATURE IN RELATION TO DATE CULTURE. A peculiarity of climate which is of considerable importance in relation to date culture is the inversion of temperature which occurs in many places in Arizona and California, and more markedly in arid regions where the date palm succeeds best. For example, in many parts of Arizona the winters are mild enough to permit date palms to be grown at an altitude of nearly 5,000 feet, and even as high as 6,942 feet at Supai. It is noticeable, however, that points very much lower frequently show temperatures sufficiently cold to injure severely or to kill date palms. For instance, at San Carlos, at an altitude of 2,456 «The pistache nut has the same advantage and can be grown with profit in place of the almond in many localities where the latter is likely to lose its fruit because of late frosts. &It is probable that the date palm is hardier than has been supposed, and that by selecting hardy sorts and wrapping them well when young, date culture can be ex- tended to many of the desert regions in the Southwest hitherto supposed to be too cold in winter for this plant. The experiments at the date garden at Tulare have shown that there is a great difference in the resistance of the various sorts to cold, the Seewah at an age of 9 years being, for instance, 12 feet high, with a spread of leaves of 15 feet, while the Sultaneh, equally old but which had been much hurt by the cold winters was only 4 feet high, with a spread of leaves of 7 feet. The experience of the winters of 1901-1902 at Tempe, Ariz., has shown that recently transplanted offshoots are hardier than has been supposed. It now becomes a matter of much importance to procure hardy sorts of date palms (probably best to be secured in the oases of Per- sia and Baluchistan) for planting in the deserts in the south western United States which have hot summers but cold winters. Fort Mclntosh, altitude 460 feet, in south- western Texas, and Fort Thomas, altitude 1,600 feet, in the valley of the Virgin River in southern Nevada, both have a summer climate hotter than that of Phoenix, in the Salt River Valley, Arizona, but at- the same time colder winters. Late sorts of dates of good quality could be matured at these places provided they could pass the winters unharmed (see pp. 126 and 134). 62 THE DATE PALM. feet, and at Tucson, at the University weather station, at an altitude of 2,230 feet, the temperature fell to 11° F. in 1891, while at Dragoon Summit, at about 4,611 feet altitude, some 60 miles to the east of Tucson and 80 miles southwest of San Carlos, the temperature is not recorded even as low as 15° F. in 1891. a In January, 1891, the temperature did not fall below 32° F. at Dragoon Summit, while at Wilcox, only 20 miles northeast, and nearly 500 feet lower, the temperature fell to 9° F. A still more striking example is shown by a comparison of the temperatures at Parker, on the Colorado River, at an altitude of about 500 feet, and at Supai, nearly 7,000 feet above sea level, some 120 miles to the north- east. In the winter of 1899 and 1900 the temperature did not fall below 26° F. at Supai, while the imperfect record at Parker shows a minimum of 23° F., that is to say, that although Supai is nearly 6,500 feet higher than Parker and is about 65 miles farther north, the min- imum temperature was actually higher at Supai in winter. Numerous similar instances could be cited in California, and the "thermal belt" along the foothills of the Sierra Nevada Mountains, adjoining the interior valley region, offers some of the most striking examples that are known of inversion of temperature. All of these anomalies are the result of a drainage of cold air to lower levels. During the night, if radiation is unhindered by clouds, as is usually the case in arid regions, the air next the ground is cooled rapidly and flows from the higher levels into the valleys below, much as water would. As the cold air flows into the plains it 'doubtless tends to flow under and to lift up the warm air; at any rate, all eleva- ted points where there is a good drainage of air show relatively high temperatures during the night, while points located in the valley floor frequently show very low temperatures, constituting an exception to the general rule that the lower the altitude the higher is the tempera- ture. It will frequently be possible to grow date palms along the foothills where it would be impossible for them to succeed in the plains a few hundred feet below. However, high summer temperatures are essential to the proper fruiting of the date palm, as will be shown in the next paragraph, and the upper limit in altitude of its culture is more likely to be set by the insufficient heat of summer than by the severit}" of cold in winter. At points situated at high altitudes, whence there is a good drainage of air, the fluctuations of temperature are less than in the plains below, and consequently the winters are warmer and the summers are cooler. In order to grow date palms at high altitudes, it will usually be necessary to search for canyons or ravines with a southern expo- sure, where the air is heated by reflection from mountain cliffs as well as by direct insolation. « All the-data as to temperature at: the various points named are from the reports of the Weather Bureau and of the State weather services of California and Arizona. HOT SUMMERS NECESSARY. 63 HOT SUMMERS NECESSARY FOR THE DATE PALM. Date palms require a definite sum of heat in order to mature their fruit properly, but the amount varies greatly for different sorts. In general the very early ripening kinds are watery and unfit for drying, being more like table grapes than like ordinary dates. They can l»e grown far to the north where the summers are not warm enough to ripen later varieties. The Wolfskill is such a date (see fig. 3, p. 31). The sorts ripening in inidseason can often be dried, but lack the sweet- ness and exquisite flavor of the late sorts, such as the Deglet Noor (see p. 33). The late sorts, and especially the one just named, require enormous amounts of heat in order to ripen properly. The Deglet Noor date is produced in the oases of southern Algeria and southern Tunis, where fortunately there are well equipped meteorological sta- tions whose records furnish a basis for a comparison of the climate there with that of American deserts, so far as records are available for the latter. It has been calculated by De Candolle05 that temperatures down to 18° C. or 6-1.4° F. have no effect on the flowering or fruiting of the date palm, and a study of the record sheets of a self-recording ther- mometer kept at Biskra in the midst of a date orchard confirmed the correctness of this assumption. In other words, this relatively high temperature is the zero point for this plant, so far as flowering and fruiting are concerned, though it is able to grow at somewhat lower temperatures. The curves shown in the accompanying diagram (fig. 7) represent in a manner plain to the eye the heat conditions of Biskra, Algeria, in the northern part of the Sahara Desert, in comparison with those of Sal ton, in the lowest part of the Salton Basin.* The curves highest up in the diagram represent the mean maximum temperatures, the curves in the middle show the mean temperatures a Geographic botanique raisonnee, I, p. 371. & The curves for Biskra for maximum and minimum temperatures are based on averages of twelve one-half years' observations by M. Colombo, summari/ed by Snpan (Petermann's Mitth., Vol. 32, 1886, Lit. ber., p. 32); forthe mean temperature, on ten years' observations by Colombo, published by Mareassan (Ann. de 1'inst. riat. agronom., Paris, 1895). The curve for the maximum temperature for Salton is based on the record for two selected years, 1893 and 1899, each having nearly the same sum of heat for the fruiting season, from May to October, inclusive, as the average of the t \\ fl ve years recorded. Prof. Alexander G. McAdie, director of the Pacific coast divi- sion of the Weather Bureau at San Francisco, kindly furnished the records, as yet unpublished, for these years. This curve is smoothed a little and is somewhat lower than the true mean maximum, as it is based on observations taken at 2 o'clock p. in., which do not always give the highest temperature which occurs during the day. The curve for the mean temperature at Salton is based on twelve years' observations published by Professor McAdie. (California Section, Climate and Crop Service, Weather Bureau, February, 1901, p. 4.) The curve forthe minimum temperatures for Salton is not based on any observations, as the minimum temperatures are not available; the mean minimum temperatures are estimated to be as far below the mean temperatures as the mean maximum temperatures are above. 64 THE DATE PALM. of the whole day, and the curves lowest in the scale show the mean minimum temperature. In every case the dotted lines represent the record for Biskra and the unbroken lines that for Salton. The months of the year are marked off horizontally and the degrees of heat are shown by the height of the curve from the base. The temperatures can be read off in Fahrenheit at the left and in Centigrade at the right. The heavy black horizontal line represents the zero point for the flow- ering and fruiting of the date, 18° C. (64.4° F.). It is evident from the first glance at the curves that Salton is much hotter than Biskra and that the daily range of temperature is much greater, and as a consequence that the mininum is lower in winter, at the same time that the mean temperature is higher. FAHR JAN. FEB. MAR. APR. MAY JUNE JULY AUG. SEPT. OCT. NOV. DEC. CENT. -H* 110- $$s ^X^ c&r s. ^ &<• /'' "^x^ \ $r •&y ^- i^ N J k \V ys bv'' / 2s > N. *2 E3E2- Ss \ \ / A* ^/ ^ \k\ \ / ~3jjS3 ^ ' -tf\£ltt ft^^^ \ \ / M W%L_. Itffej 8_ ^\ NN \ \ 80- s' y ,< gag Hf^t— S. v^ 3S \ 75* ^^ // $''4 %Z& ****.. \ v X^ \ -26" "" „-'' / 22| jjJL X s \ > s ^ „• / s tf$fad \ \ \ \ ^x^ ^** / ,' $4)'' Zero r< \>r cUztt palm N \\ \ X / ,*- ' / s \\ Vs. \ ^ fs //' \x ^ Vx^ V 55- /,' IS \ X ^*-- 60° -- +/' x\ ^-> 12° -10° £~^_ '/ \^ x^ / V ""•• / \ , -* ^x> FIG. 7. — Curves representing the average maximum, mean, and minimum temperatures at Salton, Cal., and at Biskra, Algeria. The zero point for the date palm, 18° C. (64.4° F.), is reached by the mean temperature about April 5 at Biskra, while it is passed fully three weeks earlier at Salton, or about March 12. The mean daily tem- perature rises more rapidly at Salton than at Biskra, which brings about the result that the period when the date palm flowers, which accord- ing to Fischer's calculations^ is when the mean daity temperature is between 20° and 25° C. (68-77° F.), extends from about April 20 to May 20 at Biskra, whereas at Salton it extends from about March 23 to April 20; that is to say, if Fischer's calculations are correct, the date palm will flower about a month earlier at Salton than at Biskra, « Fischer, Th. Die Dattelpalme, ihre geographische Verbreitung und culturhistor- ische Bedeutung. In Petermann's Mitth., Ergiinzungsheft No. 64, Gotha, 1881, p. 51. HEAT REQUIRED TO MATURE FRUIT. 65 although the zero point for this plant is passed by the mean tempera- ture only three weeks earlier. The mean temperature at Biskra usually remains above 18° C. (61.4° F.) from about April 5 until about November 3, some 212 days, or nearly 7 months. At Salton the period having a mean temperature above 18° C. extends from about March 12 until about November 20, or some 253 days, nearly six weeks longer than at Biskra. As has been already stated, the flowering season will probably begin a month earlier at Salton than at Biskra because of the abrupt rise of temper- ature in spring, and as the mean temperature remains above 18° C. (6i. 4° F.) nearly a month and a half longer in autumn, the season is nearly two months and a-half longer, and, moreover, is decidedly hotter throughout. It is evident that if the Deglet Noor date can mature at Biskra it can certainly ripen perfectly at Salton. AMOUNT OF HEAT REQUIRED TO MATURE THE DATE. The comparison of the sums of the daily mean temperatures gener- ally employed in determining the heat requirements of plants can be made only between regions having a somewhat similar climate, and some botanists have gone so far as to deny entirely that any trust- worthy conclusions as to the development of a plant can be drawn from estimates of its heat requirements. To say that the sum of heat decides when a plant flowers or when its fruits ripen has been held to be equivalent to asserting that the other factors of equally vital importance to the plant, such as the amount and nature of its food supply, the supply of water, the amount of light, etc., have no appre- ciable influence on its development. This criticism doubtless has much force in the case of humid regions, where a variable and capri- cious rainfall greatly influences the growth of vegetation. In rainless deserts, however, where all cultivated plants are watered artificially and where the sunshine is almost uninterrupted by clouds, the sum of heat becomes a factor of predominant importance in the life history of plants, and consequently comparisons between similar desert regions in respect to their adaptability for any given cultures may very prop- erly be made by determining the sum of heat for the critical periods of the plants in question. The amount of heat necessary to ripen the fruits of the date palm has generally been calculated by adding together the daily mean tem- peratures during the months when the dates are developing, generally from about May 1 until October 31, six months in all. In this bulletin the sum above 18° C. is counted for greater convenience in making comparisons, though generally the sum is reckoned from 0° C. The table on the following page gives the summation of effective tempera- tures during the fruiting season of the date palm for a number of points in North Africa and in the Southwestern States. 13529— No. 53—04: 5 66 THE DATE PALM. TABLE 9. — Sum of daily mean temperatures above 18° C. (64.4° F.) for fruiting period of date palm from May 1 to October 81, at the stations named. Locality. Sum of daily mean temperatures above 18° C. (64.4° F.) from May 1 to October 31. Remarks. Degrees centigrade. Degrees Fahrenheit. Algiers Algeria 652 788 1,054 1,409 1,593 1,677 1,836 1,816 1,906 2,091 2,049 2,356 2,237 2,348 2,585 2,074 2,679 3,392 2,749 2, 106 1,174 1,418 1,897 2,538 2,868 3,019 3,304 3,269 3,431 3,764 3,689 4,242 4,027 4,227 4,652 3,734 4,823 6,106 4,948 3,791 No dates ripen here. Very early sorts mature. Average of many years' observations. Dates of sorts grown usually fail to ripen. Average of 6 years' observations. Dates of the sorts now grown usually fail to ripen. Dates ripen regularly. Average of many years' observations. Many sorts of dates ripen regularly. Average of 10 years' observations. Many sorts of dates ripen regularly; date culture the lead- ing industry. Deglet Noor dates ripen but are not of the best quality. Deglet Noor dates ripened very imperfectly. Deglet Noor dates ripened very slowly and im- perfectly. Deglet Noor dates ripened well. Do. Average of 5 years' observations. Many excel- lent varieties ripen. Average of several years' observations. New thermometers.1 Average of 23 years' observations. The coolest summer recorded. Observations taken for the first time with standard Weather Bureau thermometers in the regulation shel- ters, i Average of 12 years' observations. Hottest summer recorded at Salton. Orleansville Algeria Fresno Cal . . Tucson Ariz Phoenix, Ariz. (Salt River Valley). Biskra, Algeria (Northern Sahara). Ayata, Algeria, 1890 (Oued Rirh region), Sahara. Ayata 1891 Ayata 1889 Tougo'urt, Algeria (Oued Rirh region) . Bagdad Mesopotamia Indio, Cal. (Salton Basin) ... Iiidio 1903 . . Mammoth Tank, Cal. (Salton Basin). Salton, Cal., 1903 (Salton Basin). Salton mean Salton 1897 Salton 1902 Imperial, Cal., 1902 (Salton Basin). i Until 1903 the temperature records in the Salton Basin were taken by voluntary observers from thermometers exposed without proper shelters. Mr. Bernard G. Johnson, who lives in the Salton Basin between Salton and Indio, Cal., writes as follows: " Formerly there were used cheap thermometers, placed at Indio in the shade of cottonwood trees, at Salton under an overlapping roof, and at Volcano Springs under a roof that was but slightly over- lapping. Now they have standard thermometers placed in regulation thermometer shelters, and hence the difference." As might be expected, the older records taken at Volcano Springs proved to be much too high, at Salton still too high, though somewhat nearer normal, and at Indio normal or somewhat too low when compared with the records taken in 1903 with properly protected thermometers. Station. Month. Mean temper- ature for 1903. Depar- ture from normal average. Station. Month. Mean temper- ature for 1903. Depar- ture from normal average. April °F. 69 4 °F. 9 5 Indio June . °F, 91.1 »J£ — 2.8 Salton ...do..! 72.6 -3.9 Volcano Springs . . July.... 90.9 -10.4 do 72.6 +0.1 Salton ...do.... 87.8 -11.1 May 78 5 8 3 do 94.4 — 0.1 Salton do 79.1 — 4!o Volcano Springs . . August . 95.2 - 3.5 Indio do 81.0 +0 9 Salton ...do.... 94.2 - 3.0 88 5 —7 9 Indio . ...do.... 93.1 - 0.1 Salton ...do.... 89.4 -4.4 Mr. Johnson queries: " If this year, for example, May was 8.3 degrees cooler than the average at Volcano, why was it only 4 degrees cooler at Salton, 24 miles west of Volcano and at the level of the valley, while it was 0.9 degree warmer 24 miles farther west at Indio? " Nevertheless, the sum of the daily mean temperature from May 1 for 1903 was still enough to 'mature the Deglet Noor date perfectly. A further proof of the greater sum of heat in the Salton Basin, as compared with the Salt River Valley, is given by Mr. Johnson, who states that cantaloupes ripen at least fourteen days before the Salt River Valley melons at Mesa, Ariz., and that, too, before the really hot weather begins, which occurs about the first week in June. Mr. Johnson observes that if the same proportion continues, the grow- ing season up to November 1 would give about six weeks advantage over Salt River Valley. Now the Deglet Noor date nearly matures at Tempe in the Salt River Valley and will surely ripen where it will receive such a considerable sum of heat more than in the Salt River Valley. HEAT REQUIRED TO MATURE FRUIT. 67 The records taken at Ayata,rt Algeria, in the Oued Rirh country, are of particular interest. The Deglet Noor date is there grown largely for export and the meteorological observations are taken in an oasis largely planted to this variety. Even here in the interior of the Sahara Desert (see map, PI. II, p. 76) the summers are frequently too cool to permit this choice date to ripen properly. From three years' observations it is considered that about 2,000°C. are required to ripen the Deglet Noor date satisfactorily. At Biskra the Deglet Noor is grown, but does not attain the superatively good quality which has made the dates of the Oued Rirh famous.6 It will be noticed that Phoenix is somewhat cooler than Biskra, making it doubtful whether this date will ripen there in ordinary seasons. On the other hand, there can be no doubt about the Salton Basin stations being hot enough to bring Deglet Noor dates to maturity, even at Indio, in the northern edge of the basin, and at Imperial, while at Salton the sum of heat during the coolest summer recorded there was greater than the average sum for Tougourt, and almost the same as the maximum sum for an exceptionally hot summer at Ayata, when the Deglet Noor matured- perfectly. There can then be no doubt that the Deglet Noor date will ripen fully in the Salton Basin, even when the season is exceptionally cool. The importance of this demonstration can scarcely be overesti- mated, since it renders it possible to establish in America the culture of this choice date, the most expensive of dried fruits, with certainty of success. The date palm requires very high temperatures, very much higher than those recorded by thermometers exposed in the shade, and to measure accurately its heat requirements it will probably be necessary to devise a thermometer which can be exposed to the sun and which will indicate the temperature reached by the leaves. Accordingly a summation of the maximum temperature was made for the days from May 1 to October 31, which it is thought will give a better idea of the adaptability of a climate for date culture than does the sum of the daily mean temperatures. In making this summation 18° C. (64.4° F.) was taken as the zero point, as in the preceding table, and when the daily minimum fell below that point a deduction was made for the temperatures below the zero point, where they were considered as being a setback c and as preventing the observed maximum tempera- ture from causing the growth or development it would otherwise have done. « Holland, Georges. Hydrologie du Sahara algerien, p. 416. & In the oasis of Chetma, near Biskra, the Deglet Noor date is said to ripen per- fectly, thanks to the warm spring water with which the oasis is irrigated (see p. 49). cFor example, the mean maximum for October at Biskra is 27.4° C., or 9.4° above 18° C.; the mean minimum is 16.2° C., 1.8° below 18° C. Now 9.4° is 83.93 per cent of the total daily range of 11.2°, and so instead of counting 31 X9.4=291.4° as the sum for the month, only 83.93 per cent of this sum is counted, or 244.57° C. 68 THE DATE PALM. The following table gives the results of such a summation of mean maximum temperatures from a number of points where date palms grow or can be grown: TABLE 10. — Sum of daily maximum temperatures above 18° C. (64.4° F.) for dale season, May to October, inclusive, at the stations named. Locality. Sum of daily maxi- mum temperatures. Remarks. Degrees centi- grade. Degrees Fahren- heit. Algiers Algeria 1,482 2,002 2, 337 2,593 2,662 3,049 3,068 3,295 3,666 3,990 3,898 4,059 4,010 3,931 2,667 3,604 4,243 4,668 4,773 5,489 5,523 5,932 6,599 7,182 7,017 7,306 7,218 7,077 No dates ripen. Records by Angot (Meteor. Alger.) . Very early dates can ripen. Weather Bureau records, 1897-1900. Date culture practiced, but dates inferior. Records by Angot. Early sorts can be matured . Records by Angot. Early sorts can be matured. Records' of Uni- versity of Arizona, 1892-1897. All sorts of dates grown. Deglet Noor dates not of best quality. Records of Colombo for 12£ years. Many seedling dates mature: some sorts are too late to ripen fully. Records of Weather Bu- reau, 1897-1900. Deglet Noor matures well if summers are hot; ripens imperfectly during cool years. Rec- ords of Cornu for four years, 1896-1899, read from charts exhibited at the Paris Exposi- tion, 1900. Deglet Noor dates are grown for export. Rec- ords of Angot. Interior of Sahara, one of hottest stations known. Datesareextensivelygrown. Records from Tourney, Bui. 29, Arizona Agr. Exp. Sta. Average of 5 years' records, published by Will- cocks. (Fairchild, Bui. 54, Bureau of Plant In- dustry, U. S. Dept. of Agriculture, 1903, p. 10.) Unpublished records for 1893 and 1899 furnished . by courtesy of Prof. Alex. G. McAdie. These years have the temperatures for the summer season closely approximating to the average for 12 vears recorded. Record for 1902 supplied by courtesy of Prof. Alex. G. McAdie. Do. Fresno Cal Laghouat, Algeria (extreme northern Sahara). Orl6ansville, Algeria •. Tucson Ariz Biskra, Algeria (northern Sahara). Phoenix, Ariz. (Salt River Valley). Ayata, Algeria (Oued Rirh, Sahara) . Tougourt, Algeria (Oued Rirh, Sahara). El Golea, Algeria (interior of Sahara). Bagdad Sal ton, Cal. (Sal ton Basin).. Salton 1902 Imperial, Cal., 1902 (Salton Basin). It is remarkable how nearly alike the sums of the daily maximum temperatures are for Salton and Imperial for 1902 when we consider how different the sums of the daily mean temperatures are, (See Table 9, p. 66). If the records for 1902 are correct at both points it would indi- cate a noteworthy difference in climate, the maxim urns being propor- tionally higher at Imperial than at Salton. These sums of temperatures show that the Deglet Noor date is certain to mature fully at Imperial, in the heart of the irrigated portion of the Salton Basin; this is indi- cated not only by the sum of the daily mean temperatures, but still more clearly by the sums of the daily mean maximum temperatures during the fruiting season. It is worthy of note that by this system of calculating the sum of heat is higher at Phoenix than at Biskra, whereas the order was reversed when a summation of the mean daily temperature was made (see Table 9, p. 66). This result leads one to hope that the Deglet HEAT REQUIRED TO MATURE FRUIT. 69 Noor may after all ripen in the Salt River Valley. By this method of calculating, as well as by the summation of the mean temperatures, Salton heads the list, being- the hottest desert station known. a There can be no question that the Deglet Noor and other choice late sorts will mature here and in the other parts of the Salton Basin. The advantages of excessively hot summer climates for date culture are demonstrated in the Souf country in the Sahara, a region covered with large dunes, sometimes 500 feet high, of wind-blown sand (PI. II, p. TO), lying about 50 miles east of the Oued Rirh and probably having about the same summer climate as Ayata and Tougourt. The best Deglet Noor dates are said to come from the Souf and are grown in peculiar sunken gardens excavated to a depth of from 25 to 30 or even 50 feet. These sunken gardens, called "Ghitan" or "Rhitan" (see tig. s), are dug down to within a few feet of the level of the ground water *-«*• FIG. 8.— Sunken date gardens in the sand dunes in the Oued Souf region, near El Souf, Algeria. and are large enough to contain from 0 to 100 palms, usually from 25 to 50. The sides are sloping, and composed of sand which reflects the sun's heat and light on the leaves from the sides and from below, thus intensifying the heat to such a degree that even the Arabs can not work in these gardens during the hottest weather.* In these torrid gardens the space is so valuable that the palms are not allowed to pro- « See footnote, p. 66. &No irrigation is necessary for the date palm in these gardens, as the roota reach the moist sand near the water level. The chief labor is the carrying out of the sand blown in by the wind. When the hot simoon winds of summer blow, the natives do not attempt to work during the day but commence after midnight when the temperature is lowest. So difficult is the struggle against the sand blown into the gardens by every high wind that their labor has been likened to that of ants rather than that of men. 70 THE DATE PALM. duce offshoots, which are imported f rorn the Oued Rirh country when needed to plant new gardens. A single palm may be worth from $80 to $100 arid may produce as much as 330 pounds of dates, which bring the highest price of any in the Sahara. There can be little doubt that the superior quality of these dates is due to the accumulation of heat in the still air of the sunken gardens by reflection from the bare sand of the sloping sides. In the Salton Basin the Deglet Noor date can doubtless attain the same perfection with infinitely less expense and trouble, since the higher summer temperature will give the same heat in level orchards that is reached in the sunken gardens of the Souf . EFFECTS OF WIND ON THE DATE PALM. In the large deserts there are frequently high winds which are usually very hot and dry and sometimes so violent as to carry great quantities of dust and sand. Delicate foliage is injured by such winds in two ways; first, by being lacerated by the violence of the wind and also bruised and abraded when sand is carried; second, by the drying action of the intensely hot, dry air, especially on leaves which have been torn or injured. Such winds often cause great discomfort and even grave danger to caravans in the desert. ' ' The spectacle is fright- ful, the impression most painful, the danger real; sand obscures the air and singes the face, it fills the eyes, the mouth, the ears; it hurts the throat and dries up the water skins of the native caravans, which are thereby in danger of perishing. " a Such winds, called "simoons" or "siroccos" in the Sahara, often blow several days in succession, sometimes keeping up all night. During such winds the relative humidity sometimes falls as low as 2 per cent at a temperature of 33° C., corresponding to 0.75 mm. pressure of water vapor, J whereas the mean humidity of the driest month at Paris, for example, is 57 per cent, and at Biskra 25 per cent (see p. 53). Observations made by the writer at Biskra during a sirocco at 3 o'clock p. m., May 13, 1900, showed even less humidity. The dry thermometer read 38.5° C. and the wet bulb sling thermometer 15.3° C., corresponding to a relative humidity of 2 per cent and an absolute pressure of water vapor of 1.02 mm/ Sometimes the air is so dry in the interior of the Sahara that the instruments such as have been used do not indicate the presence of any water vapor whatever. a Holland, Georges. Geologic du Sahara algerien, p. 225. &Massart, Jean. Un voyage botanique au Sahara. In Bui. Soc. Roy., Bot. de Belgique, vol. 37 (1898), I, p. 273, observations made near Ouargla at, noon, May 23, 1898; the wet-bulb sling thermometer registered 14.2° C., which gives nearly 7 per cent relative humidity by Prof. C. F. Marvin's tables (Weather Bureau Publica- tion No. 235, 1900). c Calculated by Prof. C. F. Marvin, Weather Bureau, U. S. Dept. of Agriculture. EFFECTS OF WIND. 7l Such winds have no bad influence on the date palm, but on the con- trary favor the proper maturing of the fruit in regions where the sea- son is short and some oases in northern latitudes fail to produce a crop if the hot winds do not blow frequently. a The date trunk is so strong and elastic and so firmly attached by the cord-like roots that it is an extremely rare occurrence for a palm to be broken or blown over 1>\ the heaviest gales, although the crown of leaves at the top of the slen- der stem exposes the trunk to the greatest possible strain. The loaves are very tough and strong and are very seldom torn by the wind or bruised by sand. The on\y harm heavy windstorms do is to interfere with the setting of the fruit by blowing the pollen away. This injury can usually be remedied by repollination after the storm is over. In the Salt River Valley, at Tucson, and at many other points in southern Arizona, the average wind velocity is low and wind storms are infre- quent, so the date palm has in these regions no particular advantage over other plants because of its ability to support wind and sand storms. In the Salton Basin, however, the case is different, as rather heavy winds are not uncommon, and dust and sand are often carried in consid- erable amounts. These winds are, however, certainly not so severe as in the Sahara and will in no way interfere with successful date culture. It seems, however, that in the great date region about Bassorah, at the head of the Persian Gulf, the "shamel," or hot wind laden with dust, may do great damage. Mr. Fairchild states b that ' ' if this (shamel) occurs before the dates have sufficiently matured it dries them up and covers them with dust, checking their development and soiling them so that they are refused by the European and American importers. Last year's crop (1901) was seriously injured in this way, and the export was reduced from nearly 2,000,000 cases to about 1,000,000." It is conceivable that the enormous losses occasioned in the Bassorah region by hot, dust-laden winds, which are nowhere else reported to have so deleterious an action, may be due to the peculiar character of the climate at the head of the Persian Gulf. The proximity of the sea causes the humidity to be much greater here than in most date-growing regions, and this unusual humidity may perhaps render the develop- ing dates peculiarly susceptible to injury by desert winds, possibly by rendering their surface sticky and thereby causing the dust carried by the wind to adhere to them. The cold northwest winds which often blow for several days at a time during the winter and spring in the Algerian Sahara c and the « At the oasis of Khabis in Persia dates do not ripen well unless the hot, dry, desert wind blows at least forty days during the summer. Abbot, cited by Fischer, Die Dattelpalme, p. 55. &Fairchild, D. G. Persian Gulf Dates and Their Introduction into America. Bui. 54, Bureau of Plant Industry, U. S. Department of Agriculture, p. 28, 1903. c Holland, Georges. Hydrologie du Sahara algerien, p. 416. 72 THE DATE PALM. cold north and east winds in southern Tunis a are said to hinder the pollination of the date palm. When they occur in summer they retard the maturing of the fruit and may even cause it to drop. In Seistan, in the plain of southern Persia, at an altitude of 1,300 feet above the sea level, in the same latitude and altitude as flourishing date oases in the Sahara, date culture is entirely prevented and all other fruit cultures rendered impossible except in the shelter of high walls by the " Badi sado biat," or "120-day wind,"- a violent, bitterly cold northwest wind which blows from the spring equinox until about July 20. b This wind would destroy the flowers of the date palm if they were exposed to it, and as the date palm can not easily be protected by walls, its culture is not attempted in this region, though it is followed in oases lying at higher altitudes far to the north which by their position in the shelter of mountain ranges are protected from such winds. It is pos- sible that in spring cold winds may occur in the Salton Basin, but they are probably less violent than in the Sahara, and are of course not to be compared to the ubadi sado biat" of Seistan. RESISTANCE OF THE DATE PALM TO ALKALI. The date palm has long been known to withstand large quantities of alkali/ and some have even claimed that a certain amount of salt in the soil is beneficial to its growth. ^ As to how much alkali the date palm can resist and still grow and bear fruit in profitable quantities practi- cally nothing definite is on record, notwithstanding the fact that hun- dreds of thousands of dollars have been invested by the French com- panies in plantations of date palms in the oases of the Algerian Sahara where alkali abounds. Apparently the date palm is so enormously resistant that it has not been necessary to pay much attention to the amount of alkali in the soil where it is grown. It has been planted on soil of practically all degrees of alkalinity and irrigated with all sorts «Masselot, Les dattiers des oasis du Djerid. In Bui. Direct, de 1' Agriculture et du Commerce, Regence de Tunis, vol. 6 (1901), No. 19, p. 121. & Bellew, H. W. From the Indus to the Tigris, London, 1874, p. 239. cThe term alkali is applied rather loosely to the more readily soluble saline matters which accumulate in the soils or in the water of desert regions. In spite of the name such salts are mostly neutral in reaction, consisting chiefly of chlorids, sulphates, and nitrates of the bases sodium, potassium, and magnesium. Only the carbonates of sodium and potassium, constituting the much-dreaded " black alkali," are strongly alkaline in reaction, and because of their caustic nature much more deleterious to most plants than are the neutral salts or "white alkali," which latter are injurious chiefly indirectly by rendering the soil water too concentrated a solution and thereby unfitted to nourish the roots. ^ Ibn-el-Fasel, an" Andalusian Moor, whose book, written in the twelfth century, unfortunately has been lost, is said to have given the exact amounts of salt which should be mixed with the manure for date palms. (See Cusa, Salvatore, in Archive storico siciliano, I, 1873, p. 356. ) RKSISTANCK TO ALKALI. 73 of water, from good drinking water to veritable brine containing 1 per cent of saline matters. It is the custom to provide for drainage, usually by means of open ditches, in the oases having much alkali in the soil or in the water. If the drainage is good, abundant irrigation has the effect of washing the excess of alkali out of the soil. . However, even in such situations there has been little study of the best means of preventing the accumulation of alkali or of washing it out of the soil, and many of the planters have no comprehension of its action on the date palm. INVESTIGATION OF THE ALKALI-RESISTING POWER OF THE DATE PALM IN THE SAHARA. In view of the entire absence of trustworthy data as to the alkali resistance of the date palm, the writer determined on the occasion of his last visit to the Sahara Desert in 1900 to make a study of the soils in the date plantations in order to determine the amount of alkali these soils contain and what effect it had on the growth and fruiting of the date palm when present in excessive quantities. Samples of soils were secured in five different regions in the Algerian Sahara (see map, PI. II, p. 76), representing several different methods of culture and drain- age and showing all degrees of alkalinity. Through the kindness of Prof. Milton Whitney, Chief of the Bureau (then Division) of Soils of the Department of Agriculture, who also furnished instruments for collecting and studying the soils on the spot, these samples were ana- lyzed by Mr. Atherton Seidell in accordance with the methods usually followed in the Bureau of Soils, namely, by digesting 50 grams of soil in a liter of water for twenty-four hours and then analyzing the super- natant solution. The analyses made in this manner do not represent accurately the conditions existing in the soil water, since the amount of the slightly soluble salts, especially gypsum, reported is far in excess of what could dissolve in the soil moisture, which in the rather sandy loam of most of the Sahanin oases would constitute about 8 to 15 per cent of the weight of the soil, whereas in the method followed in mak- ing the analyses about 150 to 200 times as much water was used. In this bulletin, therefore, the analyses of Mr. Seidell have been recalcu- lated in order to represent more nearly the conditions existing in the soil. The amount of calcium sulphate' thai goes into solution in the soil moisture has been estimated at 0.05 per cent in all the analyses, except where large amounts of other sulphates were in solution, when it was estimated at 0.02 percent. The amount that dissolves undoubt- edly varies somewhat, depending on the quantity and nature of the other salts present in solution. However, the amount here e>timat«-d is not far from the quantity actually present, and its inclusion in the analyses renders them much more useful than to omit the gypsum 74 THE DATE PALM. altogether, or to include the very much larger amounts reported in the original analyses.01 The solubility of gypsum in the soil moisture is difficult to estimate, especially in the presence of large amounts of other salts in varying proportions^ The researches of Doctor Cameron and Mr. Seidell,6 of the Bureau of Soils, show that in pure water at 25° C. the solubility of calcium sulphate is about 0.21 per cent, or 2.1 grams of calcium sulphate per liter of water, which would equal 0.27 per cent of gypsum. In a 1 per cent solution of common salt 0.44 per cent of gypsum is dissolved, and in a 4.9 per cent salt solution 0.75 per cent of gypsum. In mag- nesium chloride an even greater solubility was observed and in a 10.5 per cent solution of this salt 11.13 per cent of gypsum dissolves. On the other hand, salts which yield either calcium or sulphuric acid ions on solution decrease the solubility of gypsum. In a 1.54 per cent solu- tion of sodium sulphate only 0. 16 per cent of gypsum is dissolved, though in a stronger solution more is taken up until, in a 22.2 per cent solu- tion of sodium sulphate, 0.26 per cent of gypsum is dissolved. Calcium chlorid in solution depresses even more the solvent power of water for gypsum. Estimating the water content of the Saharan soil, mostly sandy loam, at 10 per cent on the average, and the solubility of calcium sulphate at 0.5 per cent (equal to 0.6 per cent of gypsum) on the average in the salts such as occur in the Fougala and Oued Rirh region of the Sahara, the amount of calcium sulphate to be counted as alkali would be 0.05 per cent of the weight of the soil. When there -were large amounts of sodium sulphate present, as at Chegga, the amounts of calcium sulphate would be much less, probably about 0.02 per cent (equal to 0.025 per cent of gypsum) of the weight of the soil.c This method of expressing the amount of alkali is the one most easily applied where the analyses are made by extracting the alkali with an excess of water, but it is very doubtful whether it gives a cor- a In most alkaline soils the presence of gypsum is advantageous by preventing the formation of the very harmful carbonates of sodium and potassium (see pp. 101 and 119) by neutralizing the poisonous effect of the salts of magnesium (see p. 89). The physical action of alkali in rendering the soil water too concentrated to support the roots of plants is, however, exerted as much by gypsum as by any other salt in solution in equal amounts. & Cameron, Dr. Frank, and Seidell, Atherton. Bui. No. 18, Bureau of Soils, U. S. Department of Agriculture, pp. 39, 40, and 46-57. cMr. Seidell's original analyses are given in every case as a footnote in order to facilitate any comparisons which students of alkali conditions may desire to make with analyses reported in other ways than has been done by the writer. As a result of this slight emendation the analyses are brought into such shape that the results may be compared, without danger of serious error, with the determinations of alkali made by the electrical method, on which data all the newest and best maps of the alkali lands of the Southwest which have been issued by the Bureau of Soils have been prepared. EESISTANCE TO ALKALI. 75 rect idea of the alkali condition of the soil in relation to crop produc- tion, since the most important factor in reference to plant growth is the degree of concentration of the soil moisture. Inasmuch as the water capacity varies greatty in different types of soils it is easily possible that ,two soils having the same percentage of alkali by weight may differ very greatly in their ability to support crop plants sensitive to alkali. Thus in a coarse sandy soil having a low water content the* concentration of the soil moisture may be three or four times as great as in a heavy clay soil having a correspondingly greater water capacity. Fortunately it is now possible to determine quickly and accurately the degree of concentration of the soil moisture with tho ingenious instrument devised by Professor Whitney and Mr. Briggs, by meas- uring the electrical conductivity of a column of soil saturated with water. a While this method shows approximately the degree of con- centration of the soil water to which the roots of plants would be exposed, it gives no indication as to the composition of the alkali, which often varies greatly in soils only a few rods apart. Inasmuch as different sorts of alkali vary greatly in their poisonous action on the roots of plants, the needs of the biologist and agriculturist would be served best by the employment of both methods, the electrical giv- ing the concentration of the soil water; the analytical, its chemical composition. At the same time a physical analysis of the soil show- ing the water capacity would be useful in forecasting the danger of an increase in alkali content through the evaporation of saline irrigation water or by a rise of alkali from the subsoil. The soils secured from the Sahara, with the exception of the one above mentioned from Biskra, were all similar in nature, being com- posed of sandy loam or fine sand. In consequence the results of the anatyses reported in this bulletin are fairly comparable one with another and are not likely to lead to an overestimate of the alkali- resisting power of the date palm, since the water capacit}^ of these soils is low, and as a result of this the concentration of the soil water is high in proportion to the percentage of alkali present in the soil. The limits of alkali resistance worked out in this bulletin are then directly applicable to the soils best adapted to date culture, viz, sandy loams, and for all other heavier soils are below rather than above the true limit/' a This method depends upon the degree of ionic dissociation, rather than the total content of dissolved substance, and gives the best physical measure of the relative concentration and toxicity of solutions of similar composition. & Very coarse sand would- have a lower water capacity than the Saharan soils here studied, but alkali leaches out of coarse sand very easily, so that in such soil a dan- gerous accumulation of alkali is not common, though if present the limits here determined for the alkali resistance of the date palm would be too high because of the excessive concentration of the soil water in proportion to the percentage of alkali present. 76 THE DATE PALM. The very unusual ability of the date palm to withstand alkali is of the utmost importance, since it permits it to be grown profitably in soils unfit for any other paying crop and where ordinary vegetation can not grow at all. The date palm is also of great value in aiding in the reclamation of alkaline lands; for once planted to dates and reg- ularly irrigated the soil improves by a washing out of the alkali if the irrigation water is of good quality and if drainage facilities exist. The importance of the alkali-resisting power of this plant is so great that the results of the examination into the alkali conditions in the Algerian Sahara are given in detail, as they constitute the most trustworthy evidence so far in existence as to the amount of alkali the date palm can stand without injury. ALKALI CONDITIONS IN RELATION TO DATE CULTURE AT BISKRA, ALGERIA. The first important oasis planted to date palms seen in entering the Sahara by the railway is at El Kantara (see map, PI. II), where a narrow gorge separates the Algerian high plateau from the Sahara, and in a few moments the train passes from one region to the other. At El Kantara, however, the date palm is chiefly valuable in furnishing a shelter and partial shade to other fruit trees, and it is at Biskra that the date palm is first seen under conditions permitting its best growth. This oasis con- tained some 95,000 palms in 1882, and now has a total of about 100,000 bearing date palms. The two near-by oases of Filiache and Chetma contain 35,000 more. Biskra is situated in a plain near the west bank of the Biskra River. The irrigation water is furnished by large springs, situated in the bed of the river, which yield about 13,000 liters, or 3,434 gallons, per minute. This water has been analyzed fre^ quently, with fairly concordant results, the content of dissolved salts being given as follows by various chemists: Vatonne, 0.216 per cent; Buvry, 0.2236 per cent; Lahache, 0.226 per cent; Moissonnier, 0.2346 per cent. The detailed analyses by Moissonnier and Buvry are as follows: TABLE 11. — Composition (in percentage, by weight] of spring water used for irrigating the oasis of Biskra, Algeria. Authority. Cal- cium carbon- ate. Magne- sium carbon- ate. Cal- cium sul- phate. Magne- sium sul- phate. Sodium sul- phate. Magne- sium chlo- rid. Sodium chlo- rid.~ Silica. Total. Moissonnier1 0. 0278 0156 0.0070 0.0621 .0448 0.0357 0. 0102 .0474 0.0894 .0878 0.0024 0.2346 .2236 Buvry 2 0. 0280 1 Moissonnier, Recueil de mem. de medicine mil., 3 ser., vol. 31, pp. 260-267. 2 Buvry, Zeitschrft. f. allgem. Erdkunde, N. F., vol. 4, p. 200. Vide Fischer, Die Dattelpalme, p. 41. In winter, when there is a flow of water in the Biskra River, the water in the irri- gating canals may contain as low as 0.075 per cent of dissolved salts, largely gypsum (0.0437 per cent), according to Moissonnier. « The very good quality of the water in winter, together with the shortage of water in summer — there being only 0.1 liter per tree per minute when 0.3 is needed (see p. 45) — favors the practice of winter and spring irrigation commonly followed in this «An analysis of the river water mixed with the spring water after a rainstorm in April, 1880, as reported by Holland, showed only 0.04 per cent of salts, nearly half calcium carbonate (0.01852 per cent). Bui. 53, Bureau of Plant Industry, U. S Dept. of Agriculture. PLATE II. •f KILOMETERS PORTION OF THE SAHARA DESERT IN SOUTHERN ALGERIA, SHOWING PRINCIPAL CENTERS OF DATE CULTURE. ALKALI CONDITIONS AT BISKRA. 77 oasis, either indirectly by growing crops needing abundant irrigation between the palms, or directly in soaking the ground about the trees. It is doubtless because of the very low alkali content of the irrigation water in winter and the only moderate content in summer that the alkali is not troublesome in this oasis, although surface flooding is never practiced, water being applied in excavations called "dahir," hold- ing a barrel or more (PI. XVII), which are made about the base of the tree (see p. -17). Biskra has clay soils of great depth « (as much as 40 feet) and this doubt- less constitutes an additional reason for irrigating by means of dahir, since such soils are difficultly permeable for water and have a great water capacity, so that if irrigation were practiced by flooding the whole surface the water would largely be evaporated or absorbed by the surface layers of the soil, and only a small proportion would ever percolate to the roots of the date palm, especially in summer, when the supply of water is scanty. Station No. 1, where soil samples were secured, was in a garden belonging to the Victoria Hotel, some 25 feet away froni a century-old date palin (see PI. XIII), and near a vigorous young Deglet Noor palm (see fig. 1, p. 16). Alfalfa and burr clover (Mfdicago denticidata) were growing where the sample was obtained. The subsoil was a stiff c]ay. The percentage of the weight of the soil soluble in 20 times its weight of water was 0.42 for the surface foot and 0.40 for the subsoil. The following salts were found by Mr. Seidell: TABLE 12. — Amount and nature of salts soluble in excess of water in soil from date garden at Biskra (expressed in percentages of the total weight of the soil) -1 Depth. Calcium bicarbon- ate. Magnesium bicarbon- ate. Calcium sulphate. Sodium chlorid. Potassium chlorid. Total. Surface foot 0.19 0.05 0.10 0 04 0.04 0 42 Subsoil (24 to 30 inches ) 15 06 11 04 04 '40 'TMs table is identical with Mr. Seidell's original analysis. Disregarding the very slightly soluble calcium carbonate, the following would rep- resent approximately the alkali content of the soil water: TABLE 13. — Per cent of alkali in soil of palm garden at Biskra, Algeria. Depth. Calcium sulphate. Sodium chlorid. Potassium chlorid. Magnesium bicarbon- ate. Total. Surface foot .-. 0.5 0.04 0.04 0.05 0.18 Subsoil (12 to 14 inches) 5 .04 .04 .06 .19 The amount of alkali present in this soil is insignificant and in no way affected the growth of alfalfa. This sample is also interesting as being a heavy clay soil of the sort which largely composes the oasis of Biskra, but which does not occur in the other oases studied. Such soils are not considered as favorable for date culture as loamy or sandy loam soils; nevertheless date palms grow very well at Biskra, although the late sorts do not ripen their fruits properly because the summer and autumn are not hot enough. Of the area surveyed by Messrs. Holmes and Means, of the Bureau of Soils, in the Salton Basin, California, 23,120 acres, or 30 per cent, is a heavy clay comparable to this sample, and half this area contains less alkali than the Biskra garden, and a quarter more contains only slightly greater quantities (0.4 to 0.6 per cent), where « Such soils are common in the Salton Basin in California. (See PI. Ill, pp. 106 and 108.) 78 THE DATE PALM. the date palm would be able to grow as well as in the Sahara oasis, since the irrigat- ing water here is of better quality than at Biskra." ALKALI CONDITIONS IN RELATION TO DATE CULTURE AT FOUGALA, ALGERIA. In proceeding west from Biskra one traverses the so-called Western Zab, & which is first seen beyond a low mountain range, the Djebel Mendjenaib, adjoining Biskra on the west. The Western Zab, or more accurately, the Zab Dahri (Map, PI. II, p. 76, and PL XV), is a flat plain, 120 to 172 meters above sea level, which slopes gently to the south or southeast. To the north the plain is limited by the foothills of the Atlas Mountains, which rise rather abruptly. Throughout the Western Zab, at least along the route followed between Biskra and Fougala (see map, PL II), there are practically no surface indications of water, the vegetation being very scanty, consisting mostly of the "Zeita" bush (Limoniastrum guyonianum), which usually indicates the presence of much gypsum in the soil where it grows (see Yearbook 1900, PL LIX, fig. 5). In extremely alkaline spots where chlorids predominate the Zeita disappears, and is replaced by saltbushes (Atriplex), sam- phires (Salicornia), etc. There occur throughout the Western Zab occasional large springs which are used to irrigate many oases situated at a somewhat lower level to the southward. Begin- ning at Farfar there is seen a most characteristic and most curious system of date culture. The young date offshoots are planted at the bottom of pits about six feet square, and from 4 to 8 feet deep (PL XV, fig 1). An inspection of a freshly made ditch, or "bir," as it is called by the Arabs, shows that the ditch is just deep enough to penetrate an impervious hardpan, composed of marl and gypsum. Below this stratum water is found and the palms are so planted that their roots can easily penetrate to the water level, and after once getting established they are able to grow without being irrigated from the surface. As the palms grow older the ditches are slowly filled up, the palms in the meantime sprouting forth roots all along the lower part of the trunk. In some cases very old trees are seen to be banked up instead of being planted in ditches (PL XIV, fig. 1). Curiously enough the trees planted in such pits are often irrigated, although their roots are in contact with water. As will be shown later on, this is doubtless done in order to aerate the subsoil and to wash out the alkali, which would otherwise be left at the surface by the evaporation of the moisture brought to the surface by capillary attraction. When irrigated, there is of course perfect drainage through the bottom of the "bir" to a practically fixed water level below. At Fougala a French company purchased an entire oasis containing thousands of old bearing date palms, and has made in addition extensive new plantations. This property comprised in 1900 some 263 hectares and contained about 18,000 bearing date palms and 6,000 young trees not yet in bearing. On this property irrigation has been practiced on an extensive scale, although the older palms were grown by planting in pits as previously described, and were irrigated when young by the Arabic method, namely, by raising water from shallow wells by means of buckets attached to sweeps ( ' ' kitara " ) c (PL XIV, fig. 2) . The wells on this property are from 9 to 12 feet deep and are from 6 to 8 feet square. They yield about 35 gallons per minute, for some three hours, by which time the water is usually exhausted. These sweeps are run at this rate by a single Arab, although on some wells there are double sweeps, and then two Arabs work side by side. The water from such wells is poured into a large receptacle called "jabia," from which it flows into irrigation ditches. In o Biskra water contains from 0.075 to 0.235 per cent of alkali and is worst in sum- mer. (See p. 76. ) Colorado Kiver water used to irrigate the Salton Basin contains from about 0.021 to 0.125 percent of salts and is best in quality in midsummer, when the flood occurs. & Marked Zibane in the map, PL II, p. 76. c See also Yearbook 1900, PL LXI, fig. 6. ALKALI CONDITIONS AT FOUGALA. 79 addition to these native wells the Companie de 1'Oucd Rirh has put down several arte- sian wells « which are some 80 meters deep and yield from 50 to 75 gallons of flowing water per minute, which is conducted directly into the irrigation ditches. This water is remarkably pure, containing very much less salts in solution than the artesian water of the Oued Rirh country or that of Biskra. A rough test of its electrical conductivity indicated the presence of about 0.085 per cent of dissolved salts. The effect of irrigation with this water is marvelous. Old date palms which had made a slow and stunted growth and which had fruited but little, at once grew luxuriantly when irrigated and began to bear heavy crops of fruit. Inasmuch as these trees had their roots in constantly moist layers of earth, the effect of irrigation was in all probability due not so much to the increased supply of water as to other actions brought about by irrigation. In the first place, the structure of the soil and the manner in which the date palms are planted in pits which penetrate the hard- pan, below which standing water occurs, hinder the aeration of the subsoil and at the same time favor the accumulation at the surface of the alkali dissolved by the capillary currents of water in ascending through the strongly alkaline soil. On the other hand, irrigation with the remarkably pure water furnished by the deep arte- sian wells would tend to have exactly the opposite effect, namely, the subsoil would be aerated by means of the water which had been flowing in surface ditches, and secondly, the watering of the date palms with an abundant supply of pure water, coupled with a perfect system of drainage by means of the holes through the imper- vious subsoil & over which the trees are planted, would bring about the washing out of the alkali from the soil, especially where the trees were irrigated frequently and with large amounts of water. The hardpan would tend to confine the alkali and prevent its rise between the trees after it was once washed out of the soil. Although the date palm can grow, as will be shown further on, in soils containing as high as 3 per cent of alkali, even when irrigated with strongly brackish water con- taining over 0.6 per cent of salts in solution — it being in fact able to endure more alkali than any other plant cultivated in the Sahara Desert — there can nevertheless be no doubt that its growth is retarded and its fruitfulness lessened by the presence of large amounts of alkali in the soil or in the irrigation water. It was noticeable at Fougala that the trees which were grown in the most alkaline parts of the oasis, and especially where surface irrigation with pure water had not been practiced, were stunted and showred a pronounced yellowish color of the leaf and especially of the leafstalk. This was later seen in the oases in the Oued Kirh country, and it would seem to be an indication of an excess of alkali beyond the amount which the trees can endure without noticeable injury. An effect of pure water similar to that observed at Fougala has been noticed at Koseir, in the Egypto-Arabian desert, on the shores of the Red Sea, wrhere Klunzinger reports c that dwarfed date palms 30 to 40 feet high grow on the very alkaline soil and were nourished by very brackish water, but yield crops of small but very sweet dates only in good years after heavy rains. The action of these heavy rains probably would be much like that of the irrigation with the pure artesian water at Fougala. «The natural springs in the Western Zab, according to Rolland (Hydrologie du Sahara) , are supplied from the same source that feed,1 the artesian wells, viz, the water carried in the cretaceous strata which are upturned in the Aures Mountains limiting the Sahara on the north and which underlie the whole northern belt of the Sahara. The water of these springs soaking into the soil feeds the superficial layer of water which directly underlies the hardpan at Fougala. Very probably this hardpan has been formed by the action of this standing water. & Professor Hilgard has noted the drainage through holes in the hardpan in the San Joaquin Valley in California. Bui. No. 83, California Experiment Station. c Klunzinger, C. B. Die Vegetation der egyptisch-arabischen Wiiste bei Koseir, in Zeitschrift d, Gesellschaft f. Erdkunde, Berlin, vol. 13 (1878), pp. 432-462. 80 THE DATE PALM. It is difficult to say how much of the beneficial effect observed in Fougala from surface irrigation is due to the better aeration of the subsoil thereby brought about. There can, however, be little doubt that the date palm is distinctly favored by a proper aeration of the soil in which it grows, since the palms at Fougala when irri- gated from the shallow wells did better than those nearby which have their roots in contact with the very same layer of water which fills these wells. Of course the identity of the water supply in the case in question does not exclude the probability of the alkali being washed out from the surface soil by abundant irrigation, even if the water used is rather brackish. Unfortunately no tests were made of the water in these surface wells, but it is undoubtedly much more alkaline than the water of the deep artesian wells. Other observations made at Ourlana in the Oued Eirh region went far to show that proper aeration of the subsoil is even more important than absence of alkali for the proper growth and fruiting of the date palm. For instance, the extremely brackish water which, flows from the drainage ditches is nevertheless used in some instances to irrigate palms planted at lower levels and without apparent injury, although such palms do not show a rapid growth (see p. 98). Station No. 1 at Fougala represents the undisturbed desert conditions (PI. XV, fig. 1). It was situated where no culture, drainage, or irrigation had been practiced, or at least not in modern times/' The samples were taken a short distance to the northeast of the ruins of an old Roman fort. The natural vegetation consisted of a scanty growth of saltbushes, samphires, and other plants able to stand much alkali. A date palm, yellow and evidently not in a thriving condition, was growing near by. The amount of alkali present in the surface crust and at various depths is shown in the following table: TABLE 14. — Per cent of alkali in undisturbed Saharan soil at Station No. 1, Fougala, Algeria.1 Depth. Calcium sulphate. Magnesi- um sul- phate. Sodium sulphate. Sodium chlorid. Potassi- um chlo- rid. Magnesi- um chlo- rid. Sodium bicarbon- ate. Total. Surface crust 0 07 0 41 1 44 9 19 0 53 0 12 11.76 Surface soil (1 to 12 inches) . 05 34 37 3 79 .29 .08 4.92 Subsoil ( 12 to 30 inches) .05 .23 1.32 .12 0.02 .08 1.82 Subsoil (30to48inches— estimated ) . (.05) (.17) (.98) (.10) (.02) (.08) (1.40) Soil (1 to 4 feet— esti- mated ) . (0.38) (1.98) (.08) (2.44) 1 Mr. Seidell's original analyses of the samples from this station are as follows: Composition. Crust. Soil, 0-12 inches. Subsoil, 12-30 inches. Alkali in soil. Composi- tion of alkali. Alkali in soil. Composi- tion of alkali. Alkali in soil. Composi- tion of alkali. Ca... Per cent. 1.65 .08 4.12 .28 5.26 5.82 .09 Per cent. 9.53 .48 23.81 1.60 30. 42 33.64 .52 Per cent. 1.39 .07 1.64 .15 3.86 2.44 .06 Per cent. 14.51 .70 17.02 1.62 40.16 25.37 .62 Percent. 1.28 .05 .54 .06 3.26 .88 .06 Per cent. 20.89 .85 8.83 1.01 53. 10 14.34 .98 Mg Na.... K SO4... Cl. HCO3 Total.. 17.30 100.00 9.62 100.00 6.13 100.00 CaSO4 . . . 5.61 .41 .53 9.19 1.44 .12 32.38 2.41 3.08 53.06 8.35 .72 4.74 .34 .29 3.79 .37 .08 49.28 3.49 3.07 39.47 3.84 .85 4.36 .23 .12 1.32 70.98 3.75 1.95 21.60 MgSOi KC1... NaCl . N£uSO4 NaHCO .08 .02 1.33 .39 MgCl2 Total 17.30 100. 00 9.61 100.00 6.13 100.00 « Similar conditions near this station are shown in Yearbook, 1900, PL LXI, fig. 4, in the background. ALKALI CONDITIONS AT FOUGALA 81 It will be noted that the most readily soluble salts, sodium sulphate and the chlorides, are largely concentrated in the surface soil. This is shown graphically in the accompanying diagram (fig. 9), in which the curves are smoothed so as to show approximately the distribution at various depths of the more important salts com- posing the alkali at this station. This distribution of alkali is the common one when there is an appreciable rain- fall, as in the northern Sahara (about 9£ inches at Biskra), but is very unlike that of the nearly rainless Salton Basin, where the subsoil often contains more alkali than the surface layers. This soil was excessively alkaline, the surface foot containing nearly one-twentieth of its weight of alkali, and the whole surface soil to a depth of 4 feet containing nearly 2.5 per cent of alkali. Thealkali is characterized by the large proportion of chlorides (amounting to 81 per cent of the total salts), of which almost all is common salt, which alone makes up nearly 4 per cent of the weight of the surface foot, or some 160,000 pounds per acre in the surface foot! Depth SURFACE CRUST. 4IN. 8IN. IFOOT IblN. 20IN. 2FEET 28IN. pe T< rC ent < ^ ; 3f A Ika iin ' ^-* tot \^1 aJM hoJLi ^ ~~- — Tto1 . : So il. 2 ..••'' / ^ *>,> &L / c r> 2 GO 1 / 1 A' / / 1 4 32IN. 3 FEET 40IN. 44IN. AUctu icor tent estirt tatec Ifor* dept rbel ow3 Otn. Common, S 'alt: fSodium, Chlorid ) Magnesium, Svdphate Glcuuber* SaJbL-(So(luum, Svuiphate) FIG. 9.— Curves showing distribution of alkali to a depth of 4 feet in uncultivated Saharan soil at Station No. 1, Fougala, Algeria. This soil is very interesting as representing practically the extreme limit of endur- ance of the date palm for this type of alkali. Unfortunately samples were not obtained down to the hardpan, but if the decrease followed the same ratio as in the Station No. 2, the amount of alkali in the subsoil at 30 to 48 inches would be about 1.42 per cent, and the average for the soil to a depth of 4 feet, 2.55 percent. Station No. 2, where the soil was sampled at Fougala, was only a few hundred feet from Station No. 1, in a young date plantation, where irrigation had been prac- ticed for three years. The samples were taken by cutting away a foot or so of the side of the pit, or " bir," in which a date palm had been planted three years before. Fresh earth was reached before the sample was taken. Hardpan was encountered at a depth of 4 feet. The appearance of the locality is shown in the background of Plate XV, figure 2. 13529— No. 53—04 6 82 THE DATE PALM. The following amounts of alkali were found: TABLE 15. — Per cent of alkali in soil of young date plantation, station No. 2, Fougala, Algeria.1 Depth. Calcium sulphate . Magne- sium sulphate. Sodium sul- phate. Sodium chlorid. Potas- sium chlorid. Magne- sium chlorid. Sodium bicar- bonate. Total. Surface foot . . 0.05 0.25 0.04 1 38 0 18 0 08 1 98 Subsoil (12 to 30 inches) . . .05 .15 .09 .09 0.05 .08 51 Subsoil (30 to 48 inches) . . .05 .07 06 .07 04 09 38 Hardpan (48 to 54 inches) .05 .04 .04 .06 .04 .08 31 Soil 1 to 4 feet .21 .54 08 83 1 Mr. Seidell's original analyses of the samples from this station are as follows: Soil, 0 to 12 inches. Subsoil, 12 to 30 inches. Subsoil, 30 to 48 inches. Com pact gypsum subsoil, 48 to 54 inches. Alkali in soil. Compo- sition of alkali. Alkali in soil. Compo- sition of alkali. Alkali in soil. Compo- sition of alkali. Alkali in soil. Compo- sition of alkali. Ca Per cent. 1.30 .05 .58 .09 3.35 .92 .06 Per cent. 20.46 .79 9.14 1.47 52.70 14.50 .94 Per cent. 1.23 .04 .06 .05 3.07 .14 .06 Per cent. 26.50 .94 1.24 .99 66.03 3.01 1.29 Per cent. 1.18 .02 .05 .03 2.90 .10 .06 Per cent. 27.19 .55 1.10 .83 66.56 2.25 1.52 Per cent. 1.08 .02 .02 .03 2.63 .06 .06 Per cent. 27. 70 .46 .51 .87 67.28 1.64 1.54 Mg Na K SO4 Cl HCO3 Total 6.35 100.00 4.65 100.00 4.34 100.00 3.90 100.00 CaSO4 4.42 .25 .18 1.38 .04 .08 69.56 3.90 2.83 21.70 .72 1.29 4.19 .15 .09 .09 89.99 3.18 1.89 2.02 4.02 .07 .07 .06 92.37 1.70 1.56 1.43 3.68 .04 .06 94.08 1.02 1.64 MgSO4 . . KCL NaCL NaoSOi NaHCO3 .08 .05 1.76 1.16 .09 .04 2.07 .87 .08 .04 2.09 1.17 MgCL Total 6.35 100.00 4.65 100.00 4.35 100.00 3.90 100.00 The results of three years' irrigation with pure artesian water is very striking. The surface crust has disappeared entirely and the amount of alkali has greatly decreased at all depths. Station No. 3 at Fougala was situated in the space between large date palms, which were in a most thriving condition as a result of eleven years' irrigation. Garden vegetables and cereals had been grown on the land for a number of years. The hardpan layer was reached at a depth of only 26 inches. ALKALI CONDITIONS AT FOUGALA. 83 TABLE 16. — Per cent of alkali in soil in old date plantation, station No. 3, Fougala, Algeria.1 Depth. Calcium sulphate. Magne- sium sul- phate. Sodium chlorid. Potas- sium chlorid. Magne- sium chlorid. Sodium bicar- bonate. Magne- sium bi- carbon- ate. Total. Surt'iuv foot 0.05 0.06 0.05 0.02 0.01 0.09 0 28 tion; soil washed out by continued irrigation. 1 Date palms barely able to | grow. Washed-out surface soil. Saharan alfalfagrowshere. Formed a solid crust on ex- posure to air. Flourishingdate plantation. [Flourishing old date planta- ( tion. 1 Dates less vigorous than at \ Ourlana stations Nos. 1 and 2. Subsoil (12 14 inches) FOUGALA, STATION NO. 1. Surface crust Surface soil (1-12 inches) Subsoil (12-30 inches) Subsoil (30-48 inches) Soil (1-4 feet) . . . FOUGALA, STATION NO. 2. Surface foot Subsoil (12-30 inches) 1 Subsoil (30-48 inches) . . . Hardpan (48-50 inches) Soil (1-4 feet) FOUGALA, STATION NO. 3. Surface foot Subsoil (12-26 inches) Hardpan (26-28 inches) Soil (1-4 feet) . .. CHEGGA, STATION NO. ]. Surface foot Subsoil at 3 feet Soil (1-4 feet) CHEGGA, STATION NO. 2. Surface foot CHEGGA, STATION NO. 3. Subsoil (4-6 feet) OURLANA, STATION NO. 1. Surface foot Subsoil (12-24 inches) Subsoil (24-36 inches) . . Subsoil (36-48 inches) Soil (1-4 feet) OURLANA, STATION NO. 2. Surface foot Subsoil (30-34 inches) Soil (1-4 feet) OURLANA, STATION NO. 3. Surface foot Subsoil (12-26 inches) Subsoil (26-30 inches) Soil (1 4 feet) ARTESIAN WATER. CHEGGA. Well at date plantation 0. 4243 0. 2082 0.0046 0.0030 0.6401 OURLANA. Puits Desveaux .2972 .3311 .0040 .0030 .6353 ANALYSES OF SAHABAN SOILS. 97 PREVIOUS AND SUBSEQUENT ANALYSES OP ALKALINE SOILS FROM THE SAHARA. Two analyses of soil from the vicinity of Ourlana are reported by Holland. « These analyses were not complete, for all the more soluble constituents are lumped as salt, which is here synonymous with alkali. The vegetable soil of a new garden (see analy- sis No. 23, in Table 34) at Tala em Mouidi, very near Ourlana (Saharan formation) , showed 6.8 per cent of alkali. Another soil (No. 24, Table 34) was from Mazer, about a mile northeast of Ourlana. Here the sample was of washed soil of a salt flat not yet under culture; it contained 3.4 per cent of alkali. The same work reports 7 per cent of alkali in the vegetable soil (No. 21, Table 34) of a garden at Tougourt, 20 miles south of Ourlana, and at Coudiat el Koda, very near Tougourt, no less than 29.5 per cent of the estimated weight of the soil (No. 19, Table 34) of an alkali flat was composed of alkali (see analysis No. 19). The same soil (No. 20, Table 34) washed for two years and put under culture contained only 0.5 per cent of alkali. TABLE 34. — Composition (in percentage by weight) of Saharan soils, collected by Holland.1 Num- ber of analy- sis. Nature of sample. Silica or quartz sand. Clay. Per- oxid of iron. Car- bonate of lime. Car- bonate of mag- nesia. Calci- um sul- phate. Salt.' Water and organic matter. Total. 14 19 20 Vegetable soil of a garden at El Golea (quaternary) . . Soil of Sebkha (alkaline flat) at Coudiat el Koda, near Tougourt (quaternary) ... Same soil as No. 19 washed for 2 years and put under culture 39.0 50.0 70 0 6.0 5.0 9 0 3.0 1.0 1 3 43.0 5.0 7 0 7.0 2.0 1 0 0.5 5.0 5 0 0.6 29.5 0 5 0.3 2.0 6 0 99.4 99.5 99 8 21 23 24 Vegetable soil of a garden at Tougourt (quaternary) Vegetable soil of a new gar- den at Tala em Mouidi (Saharan formation) Washed soil of Sebkha (salt flat) not yet under culture at Mazer (modern) 48.0 11.8 30 0 6.0 55.5 26 0 2.0 1.3 0 3 9.0 8.0 20 0 0.7 1.2 22.0 8.0 15 0 7.0 6.8 3 4 5.0 7.0 5 0 99.7 99.6 99 7 16 Soluble portion (84.91 per cent) of Saline incrusta- tion of Sebkha at El Golea (modern) .56 2.95 95 16 1 69 100 26 1 Holland, G6ologie du Sahara, analyses by Ecole des Mines, Paris. 2 All the readily soluble salts occurring in these samples are lumped as salt, which is here equivalent to alkali. None of the soils analyzed for Holland was selected with any reference to date cul- ture, and it is only from the samples secured by the writer and analyzed by the Bureau of Soils, which have been described above, that any adequate idea can be formed of the ability of the date palms to resist alkali. This power to withstand alkali is one of the most striking among the life-history factors of this tree, since, in this respect, it exceeds all other cultivated plants except possibly the cocoanut palm, which latter is not killed by sea water containing 3.4 per cent of salts in solution. 6 Mr. O. F. Cook informs the writer that on Cape Mesurado, in Liberia, a Phoenix, perhaps P. redinata, grows on the sea beach nearer to the surf than any other upright vegetation, among the stunted shrubs killed back by the salt spray. The fruit of this palm, though of inferior quality, is eaten by the natives. Hybrids should be « Holland, Georges. Geologic du Sahara. & Ehrenberg and Hempricht report that on the island of Farsan, in the Red Sea, date palms grow directly out of the crevices in the coral rock, of which the whole island is composed, and although said to be irrigated from springs it may be found that the trees are subject to occasional inundation by sea water, 13529— No. 53—04 7 98 THE DATE PALM. made between this and the common date palm, in the hope of securing alkali-resistant date palms able to mature fruit near the sea in California. Through the courtesy of Mr. Thomas H. Means, of the Bureau of Soils, the author is enabled to present the results of the analyses of soils from date-palm plantations of the Oued Rirh country in southern Algeria secured during the trip he and Mr. Thomas H. Kearney made in 1902 for the Office of Seed and Plant Introduction and Distribu- tion.« These soil samples, which were collected after the above pages were writ- ten, were obtained in the same region as those secured by the writer two years previously, and amply confirm the writer's conclusions as to the extreme resistance of the date palm to alkali. Mr. Means' s tabulation is as follows: TABLE 35. — Resistance of date palms to alkali at four stations in the Oued Rirh country in the Sahara Desert in Algeria. Chemical analysis. Estimat- Electro- ed total Location. Condition of palms. Depth of sample. lytic de- termina- tions of total Total salts. Gyp- sum. Harm- ful. alkali in soil mois- ture(gyp- sum put salts. at 0.06 per cent). « Inches. M'raier Good 0-12 4.5 Do do 12-36 1 4 Do do 36-60 .5 Ourlana Good* 13 years old 0-12 bi 5 4.36 3 45 0.71 0.76 Do do 12-36 b.36 4.02 2.20 .82 .88 Do Good* 20 years old 0-12 4.77 3.79 .98 1.03 Do do 12-36 4.46 3.89 .57 .62 Do do 36-54 4.63 3.53 1.10 1.15 Do do (1-4 ft ) .86 Ourir Fair 0-12 6.99 2.38 4.61 4.66 Do do 12-26 4.82 3.90 .92 .97 «This column has been added to Mr. Means's table, and shows the amount of alkali, counting cal- cium sulphate at 0.05 per cent in accordance with the method outlined on p. 74. These sums may be compared with the analyses reported on the preceding pages and with the alkali content of soils determined by the electric method. &In regard to the seeming discordance between the results of the determination of the amount of alkali by the electrical and chemical methods, Mr. Means writes as follows: " The apparent discrep- ancy between the total solids as determined by the bridge and by chemical analysis in the samples collected from 13-y< laboratory was colle collected from 13-year-old palms at Ourlana is due to error in sampling, for the sample sent to the lected from a different hole from the sample determined by the bridge." The amount of harmful alkali is very high in these soils, higher in fact than in any of the soils collected by the writer except at Chegga, Station No. 1, and Fougala, Station No. 1. These newest analyses demonstrate anew the remarkable alkali resistance of this wonderM palm and show that it is perhaps more resistant than the writer's soil samples seemed to indicate, and make his estimates of its probable resistance conservative, to say the least. DRAINAGE WATER FROM ALKALINE SOILS USED TO IRRIGATE DATE PALMS IN THE SAHARA. It is a remarkable fact, showing the high resistance of the date palin to alkali, that drainage water is used to irrigate date palms even in the Oued Rirh region, where the artesian water is strongly brackish as it flows from the well, and where in addition it must seep through the very alkaline soil before reaching the drainage ditches. Such palms are said to be less vigorous and to yield less fruit. There are several date plantations in the oasis of Tozeur, in the Tunisian Sahara, which are irrigated exclusively by water from the drainage ditches of gardens « See Yearbook of the Department of Agriculture, 1902, p. 573. ALKALI CONDITIONS IN SALT KIVEB VALLEY. 99 situated on higher land." These plantations are so low that drainage is impossible, and naturally the growth is poorer and the yield lower than in better situations, but it is remarkable that even date palms should be able to grow at all in such situations. ALKALI CONDITIONS IN RELATION TO DATE CULTURE IN THE SALT RIYER VALLEY, ARIZONA. A recent soil survey of the Salt River Valley region made by Thos. H. Means6 shows that there are considerable areas, perhaps 1 per cent of the land in the valley, where the amount of alkali in the soil is from 0.25 to 0.50 per cent, or enough to be dangerous for most crop plants, and much more, perhaps 5 per cent of the land, contains over 0.5 per cent where none but alkali-resistant crops can grow. Most of these alkali spots are caused by the rise of the ground water in the lowest levels, as a result of irrigation, until it comes so near the surface that moisture reaches the surface and alkali is carried up from the subsoil by the capillary currents of water. Such ground water has leached from higher levels and is often charged with considerable amounts of alkali. The water used to irrigate the Salt River Valley is diverted from the Salt River and conducted to the fields in open ditches. The river is low during summer and the water often contains a considerable amount of harmful alkali in solution. Prof. R. H. Forbes, who made a study of the water of the Salt River from August 1, 1899, to August 4, 1900, finds that from Jane 1 to August 4, 1900, the average content of soluble salts was 139 parts per 100,000, of which only 8.2 parts per 100,000 consisted of the harmless gypsum, leaving 130.8 parts per 100,000, or 0.13 per cent of harmful alkali. Professor Forbes remarks that "it is to be remembered that this year (1900) was exceptionally dry, and the waters'were consequently concentrated for a longer than usual time. Nevertheless, for a considerable portion of each year these waters are low and salty in character, and it remains true that their use (which is unavoidable) must be attended with remedial care."c Professor Forbes considers it probable that with the prevailing agri- cultural practice of Arizona the use of irrigating water containing 100 parts of soluble salt per 100,000 is likely in a few years to cause harmful accumulations of alkali. In view of this danger the great value of. the date palm is obvious, since it can support very much more alkali than is sufficient to kill other crop plants. « Masselot F. Les dattiers des oasis du Djerid. In Bui. de la Direction de 1' Agric. et du Commerce, Re"gence de Tunis, Vol. 6, No. 19, April, 1901, p. 132. & Means, Thos. H. Soil Survey in Salt River Valley, Arizona, Field Operations of the Division of Soils, U. S. Department of Agriculture, 1900, pp. 287-332. « Forbes, R. H. Bui. 44, Arizona Agricultural Experiment Station, Tucson, 1902, p. 166. 100 THE DATE PALM. As was noted on page 86, water as alkaline as this is without any direct effect on the date palm and could be injurious only by leading to the accumulation of alkali in badly drained soils after many years of heavy irrigation. A sample of surface crust from an alkaline spot south of Tempe, Ariz. (sec. 3, T. 1 S., R. 4 E.), near where the Cooperative Date Garden (Pis. XXI, XXII, and fig. 6, p. 36) is located, shows the following relative amounts of alkali soluble in excess of water (50 grams of soil to 1,000 grams of water), which may be compared with the analyses of crusts from the Sahara and from the Sal ton Basin (p. 134) : TABLE 36. — Percentage composition of alkali (soluble in excess of water) in surf ace crust from near Tempe, Ariz. a Calcium sulphate 1. 56 Magnesium sulphate 3. 04 Sodium sulphate 8. 98 Sodium chlorid J 59. 72 Potassium chlorid 12. 18 Sodium carbonate 4. 14 Sodium bicarbonate . . .10. 38 Total per cent of weight of soil 2. 56 The surface soil (1 to 12 inches in depth) from the same station shows the following amounts of alkali stated in per cents of the weight of the soil: TABLE 37. — Per cent of alkali in surface soil from Tempe, Ariz. & Calcium sulphate 0. 06 Magnesium sulphate 06 Sodium sulphate 22 Sodium chlorid 1. 53 Potassium chlorid -. 23 Sodium carbonate 06 Sodium bicarbonate . . .32 Total 2. 48 It must be remembered that in. the Cooperative Date Garden at Tempe the roots doubtless reach a subsoil containing much less than this amount of alkali. Most of the alkali spots in the Salt River Valley can be planted profitably to date palms if care be taken in irri- gating (see chapter on drainage, p. 50). Near the date garden alfalfa was killed by the rise of alkali a few years ago, and even pear trees showed evident signs of distress, while a date palm growing alongside was entirely unaffected by the alkali. « Analyses quoted from Thos. H. Means, Field Operations of the Bureau of Soils, Second Report, 1900, p. 320. & Calculated from an analysis reported by Means, 1. c., p. 320. ALKALI CONDITIONS IN THE &ALTON • BASIN.-' 101 It should be noted that the alkali occurring NUM-IHY parts 'df the Salt River Valley, represented by this sample, is of a different type from that found in the Algerian Sahara and in the Salton Basin, California. In the last-named regions the alkali is of the "white" kind and con- tains only very small percentages of carbonates or bicarbonates. In the Salt River Valley sample, on the contrary, the alkali is of the so-called "black" sort, and contains an appreciable amount of the highly poisonous sodium carbonate, which is much more injurious to most plants than is "white alkali." Black alkali is intensely alkaline in reaction, a and because of this reaction is highly corrosive to the roots of plants. It also has the property of dissolving the humus of the soil, which causes the formation of black crusts and of black spots in the fields where this type of alkali is abundant; whence the name. From the thrifty growth of the date palms in the Cooperative Date Garden at Tempe, Ariz., in soils approximating the above sample in the amount and nature of their alkali content, it is probable that the date palm is able to resist small quantities of black alkali. Further researches are, however, needful to settle this point. (See p. 120.) ALKALI CONDITIONS IN RELATION TO DATE CULTURE IN THE SALTON BASIN, CALIFORNIA. GEOGRAPHY AND GEOLOGY OF THE SALTON BASIN. The Salton Basin, or Colorado Desert, (see PL IV, p. 122, fig. 10, p. 102, and PL XVIII, fig. I),6 is a basin the center of which is far below sea level (some 263 feet below at Salton). It is surrounded by mountains on three sides, and is limited on the south by sedimentary deposits of the delta of the Colorado River which have piled up con- siderably above the sea level. The high San Jacinto Mountains on the west effectually protect the basin from the cold and humid winds from the Pacific Ocean, while the still higher San Bernardino Moun: tains form a barrier on the north that stops the cold winds that sweep across the Mohave Desert; on the east, San Bernardino and the lower Chocolate Mountains limit the basin. That part of the Salton Basin which lies below sea level was covered until comparatively recent times by the Gulf of California, which then extended much farther north than now. The Colorado River, which then flowed into the gulf near where Yuma is now situated, brought down at flood times an enormous mass of sediment, which gradually « Alkali, in spite of its name, is often composed of neutral salts, such as sulphates and chlorids, and has in consequence no pronounced alkaline reaction. (See p. 72.) &See also Pis. LXXXVII. to XCV, Means and Holmes, Soil Survey around Impe- rial, Cal., in Field Operations of the Bureau of Soils, Third Report, 1901; also Pis. XXIII to XXVI, Coville and MacDougal, Desert Laboratory of the Carnegie Institution, Publication No. 6, Carnegie Institution of Washington, November, 1903. 102 THE DATE PALM. 116' 115 35 10 o 10 zo so 40 EXPLANATION WZm AREA SHOWN IN PLATE III LOWLANDS IN COL.RIV.VALLEYi 32° 116° 115' FIG. 10.— Sketch map showing the Salton Basin and the easily irrigable lowlands in the Colorado River Valley in Nevada, Arizona, and California. The area inclosed by the dotted line is below sea level. Based chiefly on maps of Lieutenant Ives and of the International Boundary Commission. ORIGIN OF THE S ALTON BASIN. 103 built a bar across the narrow gulf and cut off the upper portion, now the Sal ton Basin, from the sea.a Barrows says:6 All this took place in very recent times. The Coahuila Indians, who to-day inhabit the upper end of the valley, have a distinct apd credible tradition of the drying up of this lake and of the occasional sudden return of its waters, and the Dieguenos, who lived at a time when the supply of water along the central portion of the valley was probably much greater than at present, raised on the naturally irrigated soil abun- dant crops of maize, melons, and beans. But slowly the valley was abandoned to aridity. Almost unvisited by rainfall, except about the edge of the mountains, the loss of the river left it cruelly dry. Low, and inclosed between heat-reflecting ranges that shut off the breezes of the ocean, it gained a temperature which is one of the highest on the globe. The windstorms that rage up the valley from the southeast have drifted great dunes of sand over certain portions, and much of the country never reached by the deposits of the lake is as black, stony, and repulsive as erup- tive rock formations in the desert can be. Apparently about the middle of the first half of the century the overflow from the Colorado was largely checked and not resumed to any extent until the year 1849. The Indians, who had lived in plenty along the central valley, were driven by the drought forever from their homes. During the high flood of the Colorado River in June and July the water breaks through its banks near Algodones, in Mexico, a few miles below Yuma, and flows westward through an old channel for some thirty miles; then, turning north into the United States, it flows through the Salton River to Salton Lake, filling up Mesquite Lake on the way. Most of the stream, however, goes on to Lake Jululu, or Volcano Lake, from which the New River flows northward to Sal- ton Lake, and the Hardy River southward to the Gulf of California (see fig. 10). The Salton and New rivers flow only during the high- est floods, but the Hardy River flows all the year, being fed by the Rio Padrones. The Maquata Basin, a region similar to the Salton Basin, and, like it, lying below sea level, lies to the west of the Cocopah Mountains in Mexico. It is usually a waterless desert, but, at times of very high flood in the Hardy River, water flows around the mountain range, creating the Laguna Maquata c (see fig. 10) in the center of the basin. This is probably the only region in Mexico which, when irrigated, will be suitable for the culture of the best sorts of dates. «Some students of this region believe that an upheaval of the region covered by the delta aided in cutting off Salton Basin from the Gulf of California. The occur- rence of mud volcanoes and of extinct craters, such as the Sierra Prieta, lends strength to the view that the piling up of such enormous masses of sediment has induced geologic changes. The old beach lines of the Salton Basin are, however, still approximately at sea level, which would go to show that there has been but slight change in the level of the region as a whole since it was cut off from the sea. (See Barrows, David P., The Colorado Desert, in National Geographic Magazine, Vol. XI, No. 9, September, 1900, p. 340.) &L. c., p. 341. c Barrows, 1. c., p. 344. 104 THE DATE PALM. The greater part of the Salton Basin is as level as a floor and almost as destitute of vegetation (see PI. XVIII, fig. 1), which renders it an exceptionally favorable region to put under irrigation, since in most places no leveling is required and very low dikes serve to retain the water. » The geographical position of Salton Basin is indicated by figure 10, its general character is shown in Plate XVIII, figure 1, and a detailed soil map, showing t}^pes of soil and the amount of alkali present, is given in Plate III, page 106. The location of the area shown in Plate III is indicated by the ruled space in figure 10, page 102. Many schemes have been broached for the irrigation of the Salton Basin since it was first surveyed in 1854. Since 1891 Mr. C. R. Rock- wood, of Los Angeles, Cal., has been making surve}Ts and persistently endeavoring to interest capital in irrigating this region. His efforts have resulted in the formation of a company which in 1901 carried the first water into the lower part of the Salton Basin. a Land and irrigation companies formed at the same time and, working in cooper- ation with the company mentioned, pushed energetically the sale and development of the land irrigated by the water, and now in 1903 some 100,000 acres are under irrigation and it is planned to extend the canals so as ultimately to irrigate most of the basin below the sea level, some 500,000 acres in all. The main diversion works are at Han Ion's Heading, some 7-J- miles below Yuma, whence the water is conducted about 8 miles to the channel of the Salton River, which is used to carry the water 60 miles to the northwest, where at the international boundary line it is turned into a 60-foot canal with a capacity of 5,000 second-feet, intended to irrigate all the lands lying between the Salton and New rivers. After entering the United States for a short distance this large canal is divided into two 30-foot canals running side by side, the object being to use one while the other is being cleaned. The courses of the lateral canals are shown in the map on Plate III. Other main canals are planned to conduct the water from the Salton channel to irrigate land in Mexico as well as lands in the Salton Basin in Cal- ifornia lying east of Salton River and west of New River b (see figure 10, p, 102). WATER SUPPLY OF THE SALTON BASIN. The greater part of the Salton Basin can be watered from the Colo- rado River, and a large area in the basin, from Calexico, on the Mexi- can boundary, to Imperial, Brawley, and northward, is now irrigated « Means, Thos. H., and Holmes, J. Garnett. Soil Survey around Imperial, Cal. In Field Operations of the Bureau of Soils, U. S. Department of Agriculture, Third Report, 1901, p. 588. & Means and Holmes, Soil Survey around Imperial, Cal., Field Operations of the Bureau of Soils, U. S. Department of Agriculture, Third Report, 1901, pp. 588, 589. WATER SUPPLY OF THE S ALTON BASIN. 105 by means of water conducted from near Yuma, as above described. Fortunately, the Colorado River water is of remarkably good quality, although this stream flows for hundreds of miles through arid regions and many of its tributaries drain highly alkaline deserts. An exten- sive set of analyses was made by Prof. R. H. Forbes for the period from January 10, 1900, to January 24, 1901," during which time the content in soluble salt of the river water at Yuma varied from 21 to 1 25 parts per 100,000, or from 0. 021 to 0. 125 per cent. During the low stages of the river in winter, early spring, and late in summer, the alkali content runs about 90 parts per 100,000. For two months (from May 25 to July 27, in 1900), during the flood caused by the melting of the snows of the Rocky Mountains, less than 27 parts of soluble salt in 100,000 were observed. On the other hand, during a smaller sud- den rise in October, due to torrential downpours on the Arizona water- shed, the alkali content rose markedly, averaging 105 parts per 100,000 from September 26 to November 19. This decided increase in the soluble salt content of the water was doubtless occasioned by the wash- ing of salts out of the desert soil into the Arizona rivers and its subse- quent drainage into the Colorado River. During the year 1900 the Colorado River water contained less than 100 parts of salts per 100,000 of water during 315 days and more than 100 parts per 100,000 during only 50 days. During the growing and fruiting season of the date palm, from April 15 to September 15, inclusive, when four-fifths of the water needful for the whole 3^ear,must be applied, the soluble salt content ranges from 0.021 to 0.068 per cent, or from 21 to 68 parts in 100,000 of water; while for two months during the flood, when water is most abundant for irrigation purposes and consequently most easily spared for washing alkali out of the soil, the alkali content is only about 27 parts per 100,000, or 0.027 per cent. A considerable part of the soluble salts held in solution consists of harmless (if not beneficial) gypsum, which varies but slightly during the year, making up from 5.6 to 8.6 parts per 100,000, which would reduce the harmful alkali content during the summer months to about 14 to 60 parts per 100,000, and to 20 parts per 100,000 during the two months of flood in May, June, and July. Such small amounts of alkali in irrigation water are without harmful influence. The relatively high purity of the Colorado River water is shown best by a comparison with that used to irrigate the flourishing date gardens of the Sahara. At Biskra the amount of soluble salt varies from 75 to 235 parts per 100,000, and is highest in summer, when the palms need most water. At Chegga, Algeria, the soluble salt « Forbes, B. H. The River Irrigating Waters of Arizona— Their Character and Effects. Bui. No. 44, Arizona Agricultural Experiment Station, Tucson, 1902, p. 202. 106 THE DATE PALM. content of the artesian water is no less than 640 parts per 100,000, and after subtracting gypsum there remain 434 parts per 100,000 of harmful alkali — 0.434 per cent, or 250 grains to the gallon. At Ourlana, Algeria, very extensive and flourishing plantations are irrigated from a flowing artesian well (Puits Desveaux), where the water contains 635 parts per 100,000 of soluble salt and 403 parts per 100,000 of harmful alkali. The Colorado River water is better than that used to irrigate the famous Salt River Valley of Arizona, and has the advantage of having the lowest alkali content in summer, whereas just the reverse is true of the Salt River water (see p. 99). The water of the Colorado River carries, both in solution and in suspension as tine silt, fertilizing materials of considerable value, con- sisting principally of potash, nitrogen, and phosphoric acid. The soils of the Salton Basin are at present so rich that they do not need the fertilizers thus carried to the land by the irrigating water, but such fertilizing substances deposited by the water will serve to keep up the fertility in the future even under heavy cropping. Even now the phosphoric acid brought by the Colorado River water (see p. 114) is doubtless decidedly beneficial to the soils of the Salton Basin, which contain but very small amounts of this very necessary plant food. SOIL CONDITIONS IN THE SALTON BASIN. The soil conditions existing in the greater part of the Salton Basin are shown by Means and Holmes, of the Bureau of Soils, a who made surveys in 1901 covering some 108,100 acres lying between the New and the Salton rivers (fig. 10 and PI. Ill), comprising the larger part of the basin as yet put under irrigation. This area is shown on Plate III. The same classes of soils and the same general condition of alkalinity prevail over the greater part of the Salton Basin.5 In the portion of the basin surveyed by Means and Holmes five types of soils were recognized. The areas occupied by these types are shown in Table 38. « Circular 9, Bureau of Soils, January, 1902, and Field Operations of the Bureau of Soils, U. S. Department of Agriculture, 1901, pp. 587-606, map 29. & The University of California also investigated the soil conditions in the Salton Basin, and in February, 1902, published a valuable report on this region (Snow, Frank J., Hilgard, E. W., and Shaw, G. W., Lands of the Colorado Delta in the Salton Basin, Bui. 140, Cal. Agr. Exp. Sta., pp. 51, with supplement by Joseph Burtt Davy, The Native Vegetation and Crops of the Colorado Delta of the Salton Basin, April, 1902, pp. 8) . Bui. 53, Bureau of Plant Industry, U. S. Dept. of Agricultur PLATE III. EXPLANATION. •Suits survewd b\- Burc/iu <>! • H CO.M.V. Contour In trnn I H) Hrrr . MAP SHOWING DISTRIBUTION OF SOIL TYPES AND OF ALKALI INTHE IMPERIAL AREA, IN!HE SALTON BASIN, CAL. SOILS IN THE SALTON BASIN. 107 TABLE 38. — Areas of different soils Mirwyed in the Salton Basin around Imperial, Cal. Soil type. Area. Per cent of area surveyed. Dnnesand Acres. 29 840 27 7 I ni perial sand 1 020 1 0 •>3 710 21 9 Imperial loam 30 410 28 0 23 120 21 4 Total -- ' ... 108 100 100 0 The alkali content of the surveyed land is shown in Table 39. TABLE 39. — Alkali content of soils surveyed in Salton Basin around Imperial, Cal. Alkali content. Area. Per cent of area surveyed. Less than 0 9 per cent Acres. 42 220 39 1 From 0 2 to 0 4 per cent 25 320 23 4 From 0 4 to 0 6 per cent 23 040 21 3 From 0 6 to 1 per cent 5 220 4 8 From 1 to 3 per cent 5 670 6 3 6 630 6 1 Dunesand consists of reddish-brown sand, rather rotten, and often mixed with small particles of flocculated soil. It is blown by the wind into small dunes, usually crescent-shaped and 2 to 10 feet high. The dunes are underlain by the heavier soils of the basin. This soil is mostly free from alkali, but the land is not now occupied for agricul- tural purposes because of the heavy expense necessary to level it to ren- der it fit for irrigation. This expense is variously estimated at from $20 to $30 an acre, and in view of the preference of the date palm for sandy soils, it may prove in future a profitable investment to level such land and plant it to the choice varieties of date palms. This dune- sand area, as may be seen from the maps, is of considerable extent. The small area of level Imperial sand is also free from harmful quantities of alkali and would be very useful for date culture. The anlount of such land is small, however, and it will probably be used for truck crops sensitive to alkali. The Imperial sandy loam soil is formed by the coarsest particles of the Colorado River deposit mixed with wind-blown sand. The sandy loam extends to a depth of 3 feet and is underlain by a loam or heavy loam. This soil will take water readily, and where level and free from alkali is adapted to cultivated crops or alfalfa. Some of the best and some of the worst lands of the valley are composed of this type. « The Imperial sandy loam occupies over one-fifth of the surveyed area in the Salton Basin and is probably the soil on which the date palm will succeed best, as it is on such land that it grows best in the Sahara. « Means and Holmes. Field Operations of the Bureau of Soils, U. S. Department of Agriculture, 1901, p. 594. 108 THE DATE PALM. About three-quarters of the area occupied by this type of soil con- tains less than 0.6 per cent of alkali, which amount is absolutely with- out harmful effect on the date palm. It will probably grow nearly as well on an additional 10 per cent of the land even without drainage, and could struggle along on 10 per cent more of the area, while if drainage were provided doubtless the whole area of sandy loam could be planted to date palms. The Imperial loam soil has a smooth surface as level as a floor and almost devoid of vegetation. It has the peculiar slick, shiny appearance often seen in localities where water has recently stood. It is the direct sediment of the Colorado River, which was deposited in strata when the area was under water. These strata are from 0.01 inch to 2 or 3 inches thick, very much resembling shale; in fact, to all external appearances being exactly similar. When water is applied, however, the soil softens up and is a red- dish, sticky loam, a little heavier than a silt loam. It is from 4 to 6 feet deep, under- lain by a clay or clay loam, and contains considerable organic matter, including an abundance of nitrogen and potash. When free from alkali it is well adapted to the growing of wheat, barley, and alfalfa. a The Imperial loam is much like the heavj7 soils in the oases at the northern edge of the Sahara, in Algeria, and is well adapted to the date palm if properly irrigated to prevent its becoming too dry and if kept in a proper state of tilth to prevent packing. This soil is very alkaline in the region surveyed in the Salton Basin, but about 60 per cent of the area covered by this soil has less than 0.6 per cent of alkali, and an additional 10 per cent will support the date palm nearly as well, making TO per cent of the land where this plant will be unhampered by alkali. The date can grow, though less vigorously, on an addi- tional 15 per cent of the area, though it may not fruit Well unless drainage be provided and some of the alkali washed out. The Imperial clay soil (PI. XVIII, fig. 1) is found as a surface soil or as subsoil at greater or less depth throughout the surveyed area. It is usually comparatively level, although in some places small hummocks have been blown up on its surface. It is this soil that surrounds both the towns of Calexico and Imperial, the only difference in the soils of the two districts being in the alkali content. The soil has been formed by the deposition of the finest sediment of "the Colorado River, and is stratified in the same way as the loam. It is a heavy, sticky, plastic soil, very much resembling the clay subsoil found in the Mississippi River Delta. When dry and in its natural state, it exists in hard cakes and lumps, which may be cut with a knife and are susceptible of taking a high polish. When wet, the lumps are very plastic and sticky, making a soil which is very refractory and difficult to cultivate, Upon drying, the soil becomes very hard and cracked. Sorghum and millet were grown this year on several hundred acres of this land in the vicinity of Calexico, and produced good crops. The sorghum, however, was the best, the yield being 6 or 8 tons to the acre. Cultivation of this clay soil will be very difficult. A similar soil is found in the Salt River Valley as a phase of the Glendale loess, and is locally known as "slick- 's Means and Holmes. Field Operations of the Bureau of Soils, U. S. Department of Agriculture, 1901, p. 595. SOILS IN THE S ALTON BASIN. 109 ens." The farmers of that neighborhood have considerable difficulty in managing this soil, and it is not as refractory as much of the Imperial clay. Either annual crops or crops which can be cultivated throughout the growing season are productive of best results on this soil, for the heavy and hard crusts need to be broken up and thoroughly pulverized occasionally. Alfalfa does not do well on such soil, for the crusts seem too hard arid the soil too dense and impenetrable to permit the constant extension of the fine rootlets so essential to permanency in an alfalfa field. Deep plowing and thorough cultivation will in a few years greatly improve this soil." Practically none of the heavy clay soil is free from alkali, but some 45 per cent of this land in the surveyed area carries less than 0.4 per cent of alkali,6 and about 25 per cent more of the area occupied by Imperial clay has from 0.4 to 0.6 per cent of alkali, where the date will succeed as well, making some 70 per cent of this soil available for the most remunerative date culture. The date palm can grow, but will fruit less on 7.5 per cent more of the clay land even without drainage, making in all about 77.5 per cent of this soil that is immediately avail- able for date culture. The date can struggle along even without artificial drainage on, perhaps, 75 per cent more of the area. The observations of Mr. D. G. Fairchild near Bassorah, on the Shat- el-Arab River, at the head of the Persian Gulf, show that these great date plantations, the most extensive in the world, are on uas pure an adobe as the clay of a brickyard," € and indicate the probability that dates may be grown successfully on any heavy soils, provided the soils be adequately drained and aerated. In the Bassorah date region the soil is automatically watered, drained, and aerated by a system of ditches which fill from the river at high tide and drain out again at low tide. In the Salton Basin and elsewhere in the United States it is prob- able that drainage ditches or tile drains will be necessary to permit the proper utilization of the heaviest clay soils. Messrs. Means and Holmes say: "Of the lands which are level enough to permit profitable irrigation 17 per cent have 0 to 0.2 per cent of alkali, and are at present safe for cultivation to all ordinary crops; 32 per cent have 0.2 to 0.4 per cent of alkali, which is risk}r for ordinary crops; the remaining 51 per cent are too alkaline to be taken up for any but alkali-resistant crops." That is to say, only 49 per cent of the irrigable land in the surveyed area of the Salton Basin is suitable for growing ordinary crops, whereas 76 per cent is available for date culture. « Means and Holmes. Field Operations of the Bureau of Soils, U. S. Department of Agriculture, 1901, pp. 595, 596. * In soils of this nature, having a very fine texture and consequently a high water capacity, a given percentage of alkali is not so injurious as in a sandy soil of low water capacity, for the reason that the alkali forms a more dilute solution in the soils which hold more water. (See p. 75. ) c Fairchild, D. G. Persian Gulf Dates and Their Introduction into America. Bui. No. 54, Bureau of Plant Industry, U. S. Department of Agriculture, 1903. 110 THE DATE PALM. To summarize, the date palm can grow on the following- areas in the surveyed region without any especial provision being made for drainage: TABLE 40. — Area of lands in the surveyed portion of the Salton Basin suitable for date culture. Kind of soil. Total irrigable area. Area where date palms will be unaffected by alkali. Area where date palms will grow and fruit without artificial drainage, but less vigorously. Area where date palms will be able to struggle along but not to fruit well unless artificial drainage is provided. Per cent of total irriga- ble area im- mediately available for date culture without artificial drainage. Additional percentage of total irrigable area where date palms can grow but not fruit well without drainage. Imperial sand Acres. 1,020 23, 710 30. 410 23,120 Acres. 1,020 17,800 18,300 16,200 Acres. Acres. 100 85 70 77.5 Imperial sandy loam 2,400 3,000 1,800 2,300 4,500 1,800 10 15 7.5 Imperial loam Imperial cl ny . . Total. .. 78,260 52,320 7,200 9,800 76 12. f) In all some 59,520 acres, or 76 per cent of the 78,000 acres of sur- veyed land level enough to permit irrigation, is immediately available for profitable date culture without artificial drainage, while the date palm will grow on an additional 12.5 per cent of the land, though it probably will not fruit well unless the soil is drained. With proper drainage almost all the surveyed area except about 3,000 acres of clay soil could be rendered suitable for date culture by washing out the alkali. Only 6 out of 156 borings made by Messrs. Means and Holmes showed a percentage of alkali so high as to be dangerous to the life of the date palm. The immense importance of date culture for this region becomes at once apparent. It is the only profitable culture that can be followed on a quarter of the irrigable area too alkaline for other crops, while the climatic, soil, and water conditions are here so favorable for the date palm (see pp. 52 to 72) that it will pay to plant the choice sorts even on the best lands where many other crops would succeed. It becomes of the greatest importance to introduce the Deglet Noor date into this region, where all the conditions combine to render its culture profitable, and where at the same time it is necessary in order to utilize a large part of the area already occupied and irrigated. a a Very recently (March, 1904), since this bulletin was sent to the Printing Office, the Department of Agriculture has established, in cooperation with the California Experiment Station, an experimental date garden in the Salton Basin at Mecca, Cal. [Mecca was called Walters until January, 1904, and is so shown on all old maps and on fig. 10, p. 102.] At the same time a large number of offshoots of the best sorts of date palms (including many of the Deglet Noor variety) were ordered from the prin- cipal centers of date culture in the Algerian Sahara. In addition, several large Deglet Noor palms are being transplanted bodily, with large balls of earth about the roots, from Tempe, Ariz. , in order to test as soon as possible the ability of this variety to fruit in the Salton Basin. ALKALI CONDITIONS AT PALM CANYON. Ill In the northern part of the Salton Basin around Indio and Walters, Cal., there are flowing artesian wells; in this and in many other respects the conditions of the Oued Rirh region in the Sahara are almost exactly reproduced. It is probable that date culture will prove even more profitable here than in the Oued Rirh country, since the summers are hotter in the Salton Basin, which will insure that the Deglet Noor variety will mature its fruit completely every year. The soils of this part of the Salton Basin have not yet been studied with reference to their alkali content, but it is known that there are large areas of land which could be irrigated by artesian wells where there is so much alkali that the growing of ordinary crops is prevented. a On such areas the culture of the date palm is likely to be the only paying industry that can be followed. ALKALI CONDITIONS AT PALM CANYON, IN THE FOOTHILLS BORDERING THE SALTON BASIN. The California fan palm (Neowashingtonia filifera) grows wild in the foothills surrounding the Salton Basin wherever the soil is sufficiently moist. In some respects the fan palm is much like the date palm, for it needs a constant supply of water at the roots, it delights in hot, dry weather, and can resist a large amount of alkali. An old fan palm produces in a good season from 50 to 200 pounds of fruit, according to Dr. Welwood Murray. The fruit is very small, of a pleasant flavor, and it is not unlike a miniature date. Natural groves of these palms as they occur in the foothills to the north of Indio are shown on Plate XIX, figures 3 and 4.6 Dr. Welwood Murray has kindly collected a series of soil samples in the groves at Palm Canyon, near Palm Springs, Cal. These samples were analyzed through the kindness of Prof. Milton Whitney, chief of the Bureau of Soils, and the results are given herewith, cal- culated in the same way as for the soil samples from the Sahara. TABLE 41. — Per cent of alkali in soils in which California fan palms were growing at Palm Canyon, California. Sta- tion. Locality and depth. Cal- cium sul- phate. Magne- sium sul- phate. Sodium sul- phate. Sodium chlo- rid. Potas- sium chlo- rid. Sodium car- bonate. Sodium bicar- bonate. Total alkali. Al A2 B C D Surface soil and crust, flow- ing water near by. 0.02 05 1.09 078 12.88 2.98 .214 .127 0.113 .156 .014 0.09 0.26 .143 .116 17.45 .66 .60 .25 5.80 Subsoil, about 2 feet deep . . . Subsoil, about 4 feet deep . . . Subsoil, sample taken from between roots of a full- grown fan palm. .04 .078 .227 .02 .266 4.52 .696 .088 Tr. .212 « Recently J. Garnett Holmes, of the Bureau of Soils, United States Department of Agriculture, has surveyed this area, and his report will soon be published. & See also Plates XXV and XXVI, in Coville and MacDougal, Desert Botanical Laboratory of the Carnegie Institution. Plate XXVI in particular gives an excellent idea of the appearance of the fan-palm oases as seen from a distance. 112 THE DATE PALM. Sample D is the most interesting, as it shows the ability of the roots of the fan palm to grow in enormously alkaline soil. A recalculation of sample D in comparison with the surface soil of Station No. 1 at Chegga, Algeria, the only sample obtained in the Sahara with so high an alkaline content, is given herewith. TABLE 42. — Per cent of alkali in soil at Palm Canyon, California, and at Chegga, Algeria. Locality and depth. Sulphates. Chlorids. Bicarbo- nates. Total. Palm Canyon, Station D, subsoil at 6 feet depth, full of palm roots 4.806 0.784 0.212 5.80 5 11 63 08 5 82 No subsoil in the Sahara or from the Salton Basin as yet reported is so alkaline as the subsoil from Palm Canyon. There are no roots very near the surface,, where the amount of alkali is greatest, at Chegga (or at the other Saharan stations), whereas the layer in ques- tion in Palm Canyon is full of roots. Prof. R. H. Forbes a has called attention to the occurrence of roots of the date palm at 6 feet in depth in "very alkaline subsoil" in the Salt River Valley, Arizona, where they were forcing their way into the calichi hardpan. The date palm doubtless can stand as much alkali as the fan palm, and it is probable that it would grow where the fan palm is now found wild. The summer heat will doubtless be less than in the lower parts of the Salton Basin, for these fan palms occur some 500 feet or more above sea level. The winters are, on the other hand, warmer at such altitudes, if there is a good drainage of cold air to lower levels (see p. 61). CHEMICAL COMPOSITION OP THE ALKALI OP THE SALTON BASIN. An analysis of a mixture of eight surface crusts was reported in 1901 by Means and Holmes, which analysis is given below alongside that of six surface crusts obtained in 1900 in the Algerian Sahara. TABLE 43. — Percentage composition of alkali in surface crusts from the Algerian Sahara and from the Salton Basin, California. Locality and sta- tion. Cal- cium sul- phate. Magne- sium sul- phate. Sodium sul- phate. Magne- sium chlo- rid. Potas- sium chlo- rid. Sodium chlo- rid. Sodium bicar- bonate. Sodium car- bonate. Sodium nitrate. Total percent weight of soil. Fougala No. 1 . Fougala No. 4 . Chegga No. 1.. . Ourlana No. 1 . Ourlana No. 2 . Ourlana No. 3 . M'raier 32.38 25.26 5.85 22.13 26.47 62.84 8.27 2.41 5.60 2.62 18.39 13.94 .66 21.86 8.35 36.71 86.49 3.08 2.69 .23 1.99 .60 1.32 1.74 53.06 28.77 4.47 51.78 55. 05 23.32 51.82 0.72 .97 .25 .80 .67 2.25 .48 17.33 15.03 64.13 14.52 18.43 5.14 56.32 0.09 4.91 3.27 9.61 15.83 Sahara, average of 7 samples Colorado Desert, average of 8 sjvmplps 26.17 9.91 9.35 9.02 621.05 .33 b2.54 1.52 30.02 38.32 32.22 .88 9.59 ft. 013 8 91 a Arizona Experiment Station, llth Annual Report, p. 156. b Wanting in some of the soils analyzed. COMPOSITION OF ALKALI, SALTON BASIN. 113 The following table shows the composition of the alkali in a few surface crusts and soils in the Salton Basin. The analyses are some of those given by Means and Holmes. a TABLE 44. — Theoretical percentage composition of alkali in soil about Imperial, Col. Soils, "3 labo- < The choicest date that reaches America and Europe, the famous Deglet Noor of the Algerian and Tunisian Sahara, is very sweet, of exquisite flavor, and is adapted to serve as a dessert fruit; it sells for more than Smyrna figs, being the most expensive dried fruit on our markets. The demand for these dates during the holidays is never- theless greater than the supply, and if they could be sold somewhat cheaper the consumption of this fruit would be enormous. v^The Salton Basin or Colorado Desert, in southeastern California, recently put under irrigation, has a hotter and drier summer climate than the Algerian and Tunisian Sahara, where the best grades of Deglet Noor dates are grown, and is, indeed, better adapted to the cul- ture of this fruit, since not only is the climate more favorable but the soils are richer and the irrigation water is of better quality. ^The date palm will prove of equal value on the more alkaline areas of other arid regions in the Southwestern States where the winters are warm enough to permit it to grow. Most regions do not have suffi- cient summer heat to mature the Deglet Noor date, and other sorts which ripen earlier must be planted. vV It is very probable that the culture of the best second-class dates, suitable for employment in confectionery and for household uses, will prove a profitable industry in the Salt River Valley, Arizona, and it is possible that the Deglet Noor variety may mature there. Even the growing of ordinary sorts, such as the oriental dates, which are imported into this country in enormous quantities, may pay in some favored regions, such as the flood-plain of the Colorado River in Arizona and California, where exuberantly fertile lands can be had cheaply, and where the annual overflow and seepage from the river render artificial irrigation unnecessary. \ Although date palms are likely to be grown first on soils too alka- line for other crops, the culture of the finer sorts promises to be a most profitable fruit industry that would warrant planting on the very best lands and the employment of the most modern horticultural methods. 142 THE DATE PALM DESCRIPTION OF PLATES. PLATE I. Old date palms at Hermosillo, northern Mexico. Orange trees, peppers, and alfalfa are growing under the palms. December, 1899. Negative by the author. PLATE II. Map of a portion of the Sahara Desert, in southern Algeria, showing the principal centers of date culture, Zibane, Oued Rirh, Oued Souf , etc. Reduced from 1 : 800,000 map of Service geographique de FArrnee, Paris. Scale 1 : 2,400,000. Localities where soil samples were secured are marked with a star. The fine lines indicate caravan routes. The railway does not yet extend beyond Biskra. PLATE III. Map showing distribution of soil types and of alkali in the Imperial area in the Salton Basin, California. Prepared by the Bureau of Soils, U. S. Depart- ment of Agriculture, in 1903. PLATE IV. Relief map of California, showing the principal regions where dates can be grown. Reduced from a drawing made after a photograph (furnished by Prof. Alexander G. McAdie) of a relief map of California exhibited at the World's Columbian Exposition, Chicago, 1893. PLATE V. Fig. 1. — Date garden in Old Biskra, Algeria. Bunches of nearly ripe fruit are seen on the taller palms; fig trees are growing underneath in the partial shade. August, 1902. Negative by Thos. H. Kearney and Thos. H. Means. Fig. 2. — Date palms at Old Biskra, Algeria. To left, two old male date palms, showing more abundant leaves and thicker trunks than the female trees beyond. Negative by the author. PLATE VI. Fig. 1. — Native gardeners (Rouara) at Ourlana, Algeria, putting date offshoots into sacks, preparatory to shipment by camel back; to the right is seen the corner of the date plantation. Soil samples (Ourlana, Station No. 1) were obtained a few rods from here, May, 1900. Negative by Charles Trabut. Fig. 2. — Caravan loaded with date palm offshoots for the Tempe garden, Arizona, starting from Ourlana northward toward Biskra, Algeria, May, 1900; negative by Charles Trabut. Fig. 3. — Final trimming of date offshoots at Algiers, pre- paratory to packing for shipment to America, June, 1900. Negative by the author. PLATE VII. Fig. 1. — Flower cluster of male date palm just emerged from sheath; flowers opening and letting pollen escape. (One-fifth natural size.) Fig. 2. — Three female flower clusters. To left, just opening, ready to pollinate; in center, pollinated, male twig tied fast; to right, ten days after pollination. (One-fifth natural size.) Fig. 3. — Male and female flowers of the date palm, magnified: Above, young fruits turning green a week or so after pollination; in middle, female flowers ready to be pollinated; below, male flowers just shedding pollen. (Three times natural size. ) Negatives by the author. PLATE VIII. Fig. 1. — Forest of old date palms at Biskra, Algeria; an Arab has climbed the tallest tree (in the background), and is pollinating the flowers, May, 1900. Negative by the author. Fig. 2. — Arab pollinating a date palm, Ramley, Egypt, March 24, 1901; a rope passed around the trunk and attached to a broad belt at the waist aids in climbing. Negative by D. G. Fairchild. Fig. 3.— Arabs demon- strating the operation of pollinating the date palm; the cluster of female flowers is partly removed from the sheath and a sprig of male flowers is just being inserted with the right hand; the fiber with which the flowers will be tied in place is held in the mouth. Negative by the author. Fig. 4. — Arabs demonstrat- DESCRIPTION OF PLATES. 143 ing the pollination of the date palm; the next stage after Fig. 1 above; the cluster of female flowers has been entirely removed from the sheath and is being tied together with a palm-leaf fiber to hold the sprig of male flowers in place. Nega- tive by the author. PLATE IX. DegletNoor dates from the Sahara Desert. (Natural size.) Photographed at Washington two months after being picked. Above, cut open date and two seeds. Negative by G. N. Collins and the author. PLATE X. Deglet Noor dates packed for the retail trade. The small paper box con- tains about two-thirds of a pound; the wooden boxes hold about four and one- half pounds. (One-third natural size.) Negative by G. N. Collins and the author. PLATE XI. Date palms growing in basin irrigated by flooding, at Bedrachin, near Cairo, Egypt. The water ranges from a few inches to several feet deep and remains standing about 6 weeks. September, 1902. Negative by Thos. H. Kearney and Thos. H. Means. PLATE XII. Fig trees growing under partial shade afforded by date palms in the oasis of Chetma, Algeria; May, 1900. Negative by the author. PLATE XIII. Date palms in garden at Biskra, Algeria. Soil samples ( Biskra, Station No. 1) were secured in the foreground. An Arab is climbing the tall palm in order to pollinate the flowers; May, 1900. Negative by the author. PLATE XIV. Fig. 1. — Date palms growing without artificial irrigation near Fougala, Algeria; at the base of the palm trunks a bank or "goorma" is seen. Fig. 2. — Shallow well with sweep "kitara" used to irrigate date palms at Fougala, Algeria. Negatives by the author. PLATE XV. Fig. 1. — Very alkaline undisturbed Saharan soil at Fougala, Algeria; a scanty growth of salt bushes and samphires is seen in the foreground near where soil sample (Fougala, Station No. 1) was taken; to left, in middle ground, young palms are seen growing in pits. Fig. 2. — Date palm in condition called "mez- noon" or crazy, showing youngest leaves dwarfed and distorted; oasis of Fougala, Algeria; May, 1900. Negatives by the author. PLATE XVI, Fig. 1. — Young date palms growing on very alkaline soil at Chegga, Algeria. A white crust of alkali is shown along the edge of the irrigation ditch. A soil sample (Chegga, Station No. 1) was secured nearby. Fig. 2. — Young date palms at Chegga, Algeria. A soil sample (Chegga, Station No. 2) was obtained in the beef of oasis alfalfa seen on the left of the drainage ditch; May, 1900. Negatives by the author. PLATE XVII. Fig. 1. — Date plantation on alkaline soil at Ourlana, Algeria, in the Oued Rirh region of the Sahara Desert. A drainage ditch is shown and to right ridges to facilitate irrigation by surface flooding. A soil sample (Ourlana, Station No. 2) was secured between the first two trees on the right. Negative by the author. Fig. 2. — Crescent-shaped excavation, " dahir," at the base of a date palm, to hold irrigation water, Biskra, Algeria. Offshoots ready to remove are seen at the base of the trunk. Negative by the author. PLATE XVIII. Fig. 1. — View in the Salton Basin, near Imperial, Cal., looking south- ward, showing level, bare desert land, with almost no trace of vegetation; Signal Mountain, in Mexico, in the distance; January, 1901. Fig. 2. — Shore of a dry, salt lake, Chott Merouan, between Chegga and M'rai'er, Algeria, with salt-loving vegetation; in the distance a mirage simulates a vast sheet of water, with remote islands covered with bushes. Negative by the author. PLATE XIX. Fig. 1. — A neglected Egyptian date palm growing without irrigation in the Salton Basin, near Indio, Cal., November, 1899. Fig. 2.— Old date palms showing reflexed, dead leaves growing at Hermosillo, northern Mexico; orange 144 THE DATE PALM. trees grow under the palms; arid hills form the background; December, 1899. Fig. 3. — Fan palm, showing persistent dead leaves clothing the trunk, near Indio, Cal. Fig. 4. — Group of fan palms growing wild in a dry ravine near Indio, Cal., November, 1899. Negatives by the author. PLATE XX. Fig. 1. — Old date palms growing at San Diego Mission, near San Diego, Cal. Negative by Park & Co., Los Angeles. Fig. 2. — Seedling date palm, showing bunches of nearly ripe fruit, growing without artificial irrigation in the flood -plain of the Colorado Biver, near Yuma, Ariz. ; planted by Mr. Hall Han- Ion (who stands beneath), November, 1899. Negative by the author. PLATE XXI. View in Cooperative Date Orchard at Tempe, Ariz., showing growth made in two years by offshoots imported from North Africa in 1900. Photo- graphed December 31, 1902, by Prof. R. H. Forbes. PLATE XXII. Three-year-old Deglet Noor date palm in fruit, growing in the Coop- erative Date Orchard at Tempe, Ariz., from an offshoot imported from the Sahara Desert in July, 1900. Photographed August 27, 1903, by W. W. Skinner. Bui. 53, Bureau of Plant Industry, U. S. Dept. of Agriculture. PLATE V. FIG 1.— FRUITING DATE PALMS AT OLD BISKRA, ALGERIA, WITH FIG TREES GROWING UNDERNEATH, AUGUST, 1902. FIQ. 2.— DATE PALMS AT OLD BISKRA, ALGERIA. Two LARGE MALE TREES AT LEFT. Bui. 53, Bureau of Plant Industry, U. S. Dept. of Agriculture, PLATE VI. FIG. 1.— NATIVE GARDENERS (ROUARA) AT OURLANA. ALGERIA, PREPARING DATE OFFSHOOTS FOR SHIPMENT BY CAMEL BACK. FIG. 2.- -CARAVAN LOADED WITH DATE PALM OFFSHOOTS FOR ARIZONA, STARTING FROM OURLANA NORTHWARD, MAY, 1900. FIG. 3.— FINAL TRIMMING OF DATE OFFSHOOTS AT ALGIERS PREPARATORY TO SHIPMENT TO AMERICA, JUNE, 1900. Bui. 53, Bureau of Plant Industry, U. S. Dept. of Agriculture. PLATE VII. FIG. 1.— FLOWER CLUSTER OF MALE DATE PALM JUST EMERGED FROM SHEATH AND LETTING POLLEN ESCAPE. FIG. 2.— THREE FEMALE FLOWER CLUSTERS. FIG. 3.— MALE AND FEMALE FLOWERS OF THE DATE PALM, MAGNIFIED. Bui. 53, Bureau of Plant Industry, U. S. Dept. of Agriculture. PLATE VIII. FIQ. 1.— FOREST OF OLD DATE PALMS AT BISKRA, ALGERIA, SHOWING ARAB POL- LINATING FLOWERS. FIG. 2.— ARAB POLLINATING A DATE PALM RAMLEY, EGYPT, USING A ROPE AND BROAD BELT IN CLIMBING. FIG. 3.— ARABS DEMONSTRATING THE POL- LINATION OF THE DATE PALM. SPRIG OF MALE FLOWERS BEING INSERTED. FIG. 4.— CLUSTER OF FEMALE FLOWERS BEING TIED TOGETHER TO HOLD THE SPRIG OF MALE FLOWERS IN PLACE. Bui. 53, Bureau of Plant Industry, U. S. Dept of Agriculture. PLATE IX. DEGLET NOOR DATES FROM THE SAHARA DESERT (NATURAL SIZE). Jul. 53, Bureau of Plant Industry, U. S. Dept. of Agriculture. PLATE X. , • v DEGLET NOOR DATES PACKED FOR THE RETAIL TRADE. Bui. 53, Bureau of Plant Industry, U. S. Dept. of Agriculture. PLATE XI. DATE PALMS GROWING IN BASIN IRRIGATED BY FLOODING AT BEDRACHIN, NEAR CAIRO, EGYPT, SEPTEMBER, 1902. Bui. 53, Bureau of Plant Industry, U. S. Dept. of Agriculture. PLATE XII. FIQ TREES GROWING UNDER PARTIAL SHADE AFFORDED BY DATE PALMS, OASIS OF CHETMA, ALGERIA. Bui. 53, Bureau of Plant Industry, U. S Dept. of Agriculture PLATE XIII. ARAB CLIMBING TALL PALM IN A GARDEN AT BISKRA, ALGERIA, TO POLLINATE THE FLOWERS, MAY, 1 900. Bui. 53, Bureau of Plant Industry, U. S. Dept. of Agriculture. PLATE XIV. FIG. 1.— DATE PALMS GROWING WITHOUT IRRIGATION NEAR FOUGALA, ALGERIA. FIG. 2.— SHALLOW WELL USED TO IRRIGATE DATE PALMS AT FOUGALA, ALGERIA. Bui. 53, Bureau of Plant Industry, U. S. Dept. of Agriculture. PLATE XV. FIQ. 1.— VERY ALKALINE UNDISTURBED SAHARAN SOIL AT FOUGALA, ALGERIA. YOUNG PALMS GROWING IN PITS. FIG. 2.— DATE PALM IN DISEASED CONDITION CALLED "MEZNOON, CAUSED BY EXCESS OF ALKALI, FOUGALA, ALGERIA. Bui 53, Bureau of Plant Industry, U. S. Dept. of Agriculture. PLATE XVI. FIQ. 1.— YOUNG DATE PALMS GROWING ON VERY ALKALINE SOIL AT CHEGGA, ALGERIA. FIG. 2. -YOUNG DATE PALMS AND SAHARAN ALFALFA AT CHEGGA, ALGERIA. Bui. 53, Bureau of Plant Industry, U. S. Dept. of Agriculture. PLATE XVII. FIQ. 1.— DATE PLANTATION ON ALKALINE SOIL AT OURLANA, ALGERIA. FIG. 2.— CRESCENT-SHAPED EXCAVATION AT THE BASE OF A DATE PALM TO HOLD IRRIGATION WATER, BISKRA, ALGERIA. Bui. 53, Bureau of Plant Industry, U. S. Dept. of Agriculture PLATE XVIII FIG. 1.— VIEW IN THE SALTON BASIN, NEAR IMPERIAL, CAL., SHOWING LEVEL, BARE DESERT SOIL. FIG. 2.— SHORE OF A DRY SALT LAKE, CHOTT MEROUAN, BETWEEN CHEGGA AND M'RAIER, ALGERIA. Bui. 53, Bureau of Plant Industry, U. S. Dept. of Agriculture. PLATE XIX, FIQ. 1.— A NEGLECTED EGYP- TIAN DATE PALM GROWING WITHOUT IRRIGATION IN THE SALTON BASIN, NEAR INDIO, CAL. FIG. 2.— OLD DATE PALMS AT HERMOSILLO, NORTHERN MEXICO, WITH ORANGE TREES GROWING UNDERNEATH. FIG. 3.— FAN PALM SHOWING DEAD LEAVES CLOTHING TRUNK, NEAR INDIO, CAL. FIG. 4.— GROUP OF FAN PALMS GROWING WILD IN A DRY RAVINE, NEAR INDIO, CAL. Bui. 53, Bureau of Plant Industry, U. S. Dept. of Agriculture, PLATE XX, FIQ. 1.— OLD DATE PALMS GROWING AT SAN DIEGO MISSION, NEAR SAN DIEGO, CAL. FIG. 2.— SEEDLING DATE PALM WITH NEARLY RIPE FRUIT, GROWING WITHOUT IRRIGATION IN THE FLOOD PLAIN OF THE COLORADO RIVER IN CALIFORNIA. Bui. 53, Bureau of Plant Industry, U. S. Dept. of Agriculture. PLATE XXI. o Bui. 53, Bureau of Plant Industry, U. S. Dept. of Agriculture. PLATE XXII. THREE-YEAR-OLD DEGLET MOOR DATE PALM IN FRUIT, GROWING IN THE COOPERATIVE DATE ORCHARD AT TEMPE, ARIZ., FROM AN OFFSHOOT IMPORTED FROM THE SAHARA DESERT IN JULY, 1900. PHOTOGRAPHED AUGUST, 1903. ND.EX. Page. Aeration, imperfect, danger in date culture, note 121 necessity to roots of date palm 50 of soil about date palm, effect, notes 78, 80 importance in irrigation of dates 47 Age. See Bearing age. Al Shelebi, Medina date, description 40 Alfalfa, killing by alkali near date garden at Tempe, Ariz., note 100 Saharan, as crop in alkaline soil in date orchard 23, 87, 115 Algeria, alkali conditions in relation to date culture 76-99 bearing age, continuance and yield of date palms 26 Fougala, unusual drainage conditions in date growing 51 irrigation of date with warm water, remarks 49 M'Zab date region, valuable dates 37 records of atmospheric humidity and rain in date regions 55 shipment of date offshoots to Arizona 21, 42 sum of mean maximum temperature in date season 68 sum of mean temperatures in date region 66 temperature curves in date region 63-64 Alkali at Palm Canyon, near Sal ton Basin, date region Ill black, effect on plant roots and on humus 1 01 resistance of date palm 119-120 cause of disease of dates 116, 120 comparison in water and soil at two Algerian stations 95 crops resistant, notes 23, 87, 115, 121 destruction of young date plants, and remedy therefor 21 effect in clay soil, note 109 on seedling date palms, caution 18 electrical determination in soil 75 excess, effect on date palm 79, 83, 116, 120 explanation of term in connection with date culture 72 freedom of land near Colorado River 130 in Colorado River water, remarks 1 05 relation to date culture in Salt River Valley, Ariz 99-101 soil at Fougala, Algeria, graphic representation 81 resistance of date palm, note 11 soils, study and analyses to determine amount 73 surface soil, relation to date growing 117 injury to date palms in Sahara •- 83, 86, 118 nitrates in Sahara; in Salton Basin 85, 113 relation to date culture in Salton Basin, Cal 101-114 removal by irrigation and drainage 78 resistance of date palm 72-121 importance, remarks 76 limits -- 115-121 summary 141 rise, possible benefit to date palm ' 117 Salton Basin, chemical composition 112 treatment for modification in date culture 47 Alkaline lands, superior value of date for cultivation 121 soils from Sahara, analyses other than in present publication 97 subsidiary cultures with date plantations 115 water, use in irrigation of date palm 50 Amaree, early date, note 31 13529— No. 53—04 10 145 146 THE DATE PALM. Page. Amreeyah date, note 129 Analyses of Saharan soils for alkali, method 73 soils and waters of date regions for alkali, tables 76, 77,80,82,83-89,91-98 in Arizona for alkali 100 Salton Basin, Cal., for alkali 107-113 Arab cultivators, management of date palm offshoots 15 Arabia, dates of promise for United States 40 Khalas date from Hassa. .. 36 Arabs, date cultivation, notes 17 drying and packing of dates 30 planting of date palm, notes 22 practice of keeping pollen 28 skill in climbing date palm and pollinating flowers 27 watering of young date palm offshoots 21 Areshtee date, large yield, note 26 Arid regions of Southwest, suitability for date growing 11 United States. See Arizona, California, etc. Arizona, amount of water needed in irrigation of date 46 atmospheric humidity, records 53 bearing age of date palm 25 character of male dates 20 cooperative date garden, notes 41, 128 date culture, probable success 126-133 prospects 13 dates to be secured 38 varieties, very large collection at date garden 128 early importation of dates 41 growing of dates, present 32, 128-129 insufficiency of heat for seedling dates, note 18 notable yields of dates 26 number "of male date palms, note 23 peculiarity of cold air drainage in relation to date 61 profits of date culture, estimates 137 rainfall, records 53, 55, 56, 57 ripening of Deglet Xoor date, doubtfulness 67 Salt River Valley, alkali character, remarks 101 in relation to date culture 99-101 second importation of date offshoots 42 seedling dates of value 32, 128-129 summer temperatures, sum 66 Tempe and Salt River Valley, drainage problem 51 introduction of Dakar male date palm. 24 planting of Deglet Noor dates 35 temperature variations 50, 00 temperatures, mean and mean maximum, sums 66, 68 University, establishment of date garden 41 warmth o'f water in irrigation of dates Yurna, climatic peculiarities, relation to date growing 50 Artesian wells in Salton Basin, proposed use for irrigation Ill irrigation in Algeria, remarks; analysis of water 90, 91 of date palms " 121 use in irrigation of date in Sahara, notes 44, 45, 79, 82, 84 warm water for irrigation of dates 49 Assyrians, cultivation and use of dates discovery of pollination of dates 26 Atriplex semibaccata" saltbush, resistance to alkali 121 Bagdad, dates of promise for United States 39-40 Baluchistan, dates and date region Barley as crop in alkaline soil in date orchard 23 resistance to alkali, note 115 Barrows, David P., remarkson Colorado desert 103 Bassorah, date exports, notes -x soil and cultivation 109 Bearing age of date palms, discussion; note 25, 136 continuance, of date palm 26 INDEX. 147 Page. Ben Chabat, Arab, remark on distance apart in planting date palms 22 Bent Keballa date, notes 32, 37 Bennet date, notes 32, 128 Biskra, Algeria, alkali conditions in relation to date culture; clay soils. . . 76, 77 date region, temperature curves 63-64 evaporation records ; irrigation practice 46, 47 Black alkali. See Alkali. Blooming of date trees, season and manner (see also Flowering) 16, 27, 54 Botanical relations and characters of date palm 14-16 4 ' Boussaafa' ' or ' ' Meznoon' ' disease of date from alkali 116 Briggs, L. J. , devising of instrument for determining soil moisture 75 BuHafs date, note 39 Bud of date palm, importance 14 Burton, Pilgrimage to Mecca, remarks on dates 40 Calcium sulphate and chlorid, relations in soil water of Sahara 74 Calexico, outlook for date growing, notes 104, 108 California and Arizona, rainfall and irrigation (see also Salton Basin) 49 date culture, probable success 122-125 fig growing, remarks 14 Lower (Mexico) , date production 135 peculiarity of cold-air drainage in relation to date culture 61 Salton Basin, conditions favorable to date growing 12 seedling dates, experiments 20 Camels, relation to date culture in Sahara 17 Canary Island palm, possible use in hybridizing 125 Carbonates in Salton Basin soil, showing of analyses 112, 113 soil in Arizona as shown in analysis 100 resistance of date palm 119 Chegga, Algeria, comparison of soil and water with Ourlana, Algeria 95 Chlorids in Salton Basin soils 112, 113, 114 soil in Arizona, as shown in analyses 100 maximum and injury, in Sahara, note 87 resistance of date palm 118 Clay soil, alkali, effect on date palm 109 soils, use for dates, notes 77, 108, 109 Climate, California, relation to date culture 122-125 conditions favorable for date growing, notes 11 for date palm, humidity 52-58 sunshine and heat 58-70 summary 141 for date palm, ideal 56 hot summer, advantages for date growing 63-70 of Salton Basin, remarks 112 Coachilla date, seedling, description 31 Coast region, southern California date culture, chances of success 125 Cold, effect on date (see also Climate, Temperature) 21, 49, 59, 60, 61, 133 Colorado Desert. See Salton Basin. River flood, effects 50,103,105,129 peculiar climatic conditions, relations to date growing 50 quality of water, remarks 105, 106 Valley, date culture, probable success 123, 129-133 Yuma, similarity in alkali to Sahara 87 Cook, O. F., report of dates in Morocco and Liberia 39, 97 suggestion as to use of dry dates 31 Crop plants, resistance to alkali, limit, note 121 Crops, garden and field, in vacant space in date orchard 22 with dates on alkali soils, remarks 115 Cuinet, note on Khalas date 36 Cultivation of date, suitable climate and soil; work required 11, 25 Curing, gathering, and packing dates 29-30 Dakar majahel, male date palm, introduction and value for pollination 24 Date, Bearing, age 25, 136 culture, importance of life history study (see alxo Date growing) 139-141 in western Zab, peculiar system 78 Mexican competition, freedom from danger 134-136 148 THE DATE PALM. Page. Date, culture, profits (sec also Date growing) 136-138 regions of United States of probable success 122-125 (fruit), description 17 garden, cooperative at Tempe, Ariz 42, 128 experimental at Mecca, Cal 110 gardens, sunken, of Souf country, Sahara, remarks 69 growing, care of tree, pollination, gathering, curing, and packing dates. . . 25-30 in United States, types and varieties of dates suitable 30-44 season, water supply in Salton Basin 105 thinning of bunches on tree (see also Date culture) 28 palm, alkali resistance, discussion 115-121 amount of water necessary in irrigation 44 and dates, care, discussion *. 25-30 general remarks on conditions in United States 11-13 areas in Salton Basin for growing 110 as shelter for other fruit trees 43 destruction by rain at Moorzook, Fezzan, Sahara 118 drainage, discussion . . ., 50-52 effect of excess of alkali 79, 83, 116, 120 effects of atmospheric humidity and rain, discussion 52-58 wind, discussion 70-72 heat requirements, discussion 58-70 irrigation, discussion 44-50 necessity of sunshine, and heat requirements 58 offshoots, successful shipment 20-21 propagation 18-25 resistance to alkali 72-121 usefulness and botanical characters, etc 14-17 plantations on alkaline soils, subsidiary cultures 115 variation of heat requirement for different sorts 63 varieties for cultivation in Arizona 32, 128, 129 Dates, early sorts from Sahara for United States 32 finest grades, shortness of supply 138 gathenng, caring, and packing 29-30 of commerce, varieties, remarks 38 importance for United States, names and notes 39, 40 ordinary, probable success of culture; summary 132, 142 Persian Gulf, importation into United States, note 132 promising varieties introduced into United States 37 Saharan, importation into United States 41 soft and dry, notes 20 types, three, remarks 30-31 De Candolle, statement of lowest temperature for date palm 63 Death Valley, date culture, chances of success 122 Deglet Noor date, certainty of ripening in Salton Basin 67 derivation of name 36 disease, Boussaafa 116 high quality, summary 33, 141 notes. 30, 41, 58, 63, 68, 69, 70, 89, 110, 116, 122, 123, 128, 133, 136, 137 quality, grades, prices, yield, requirements in growing, etc. . 33-36 Salt River Valley, for growing 128 Salton Basin, for growing 67 shortness of supply. 138 yield, prices and profits 136 Desert regions, records of rainfall (see also Sahara, etc. ) 57 Disease, date palm, from alkali 116 ' ' Merd el Ghram ' ' due to bad drainage 120 freedom of date palm 137 Distances between trees in planting dates 22 Drainage, bad, cause of disease in date palm 120 connection with irrigation in Sahara 78, 86 for the date palm, discussion 50-52 in Colorado Valley, necessity except in date culture 131 use in Salton Basin in date culture, note .' . 110 value in alkali lands for date culture, note 73 wrater from alkaline soils, irrigation of date in Sahara 98 "Dry dates," description 31 INDEX. 149 Page. Egypt, dates, notes '32,39,41,129 irrigation by flooding, remarks 48 Egyptians, ancient, cultivation of date, notes 17 Electricity, use in soil investigations, notes 75, 79 Evaporation, relation to irrigation of dates 46 Exportation of dates, manner and importance 14 Fairchild, D. G. , description of irrigation and drainage system 48 observation of date soils on Persian Gulf 109 packing dates on Persian Gulf 137 opinion as to Bagdad, Khalas and Mozaty dates 37, 38, 40 Fan palm in Salton Basin, fruit like date; alkali resistance Ill, 112 Fard date, exports to United States, note 38 Female flowers of date, description and method of pollination 27 differences from male flowers 19 Fig growing in California, reniarks 14 under date palm 44 Fischer, Th. , calculations of temperature for date flowering 64 remarks on Mozaty date 37 Flooding as method of irrigation, probable value in date growing 48 Flower clusters of date, description and number 26-27 Flowering of date palm, lateness as safety from frost (see also Blooming) 61 lowest temperature limit 63 Flowers and fruit of date, disastrous effect of rainy weather 54 date, effect of pollination on value of fruit 28 of date palm, male and female, growth; distinguishing marks 16, 19 Forage crops with dates on alkali soils, notes 115 Forbes, Prof. R. H. , experience with date palms in alkali soil 18, 21, 42 observation on date palm roots 112 ripening of dates, artificial, method 135 Rhars date, observation 32 study of water and irrigation 99, 105 Fougala, Algeria, alkali in relation to date culture 78-84 French, planting of date palm in the Sahara, notes 22 Fritsch, G. , conclusion as to germination of date 19 Frosts, escape of date by late flowering 61 Fruit and flowers of date, disastrous effect of rainy weather 54 date, heat required for maturing 65-70 of date palm, need of dry air for proper development 52 .trees, shelter of date palm 43 Fruiting of date palm, effect of pollination on value of date 28 lowest temperature limit 63 necessity of high temperature 62-65 Fruits for growing, with dates on alkali soils, notes 115 Fukus date, note 39 Gardens, date, experimental in Arizona and California 42, 110, 128 sunken, of Souf, Sahara, description 69 Gathering, packing, and curing dates 29-30 Geography and geology of Salton Basin, California 101 Geological Survey, estimate of irrigable lands on Colorado River 130 Geology and geography of Salton Basin, California 101 Germination of date palm (seed), need of water 19 Gila Valley, Arizona, date culture, probable success, notes 126, 133 Gypsum in Saharan soils, note 73 solubility in soil moisture 74 use in reclamation of black alkali lands 119 Habitat, natural, of date palm, indications ' 19 Malawi date, note 38 Hamraya date, note 26, 37 Hanlon date plantation, climatic peculiarities 50 Hardpan, drainage in date lands 51, 78 Hayani date, note 32 Heat, amount required to mature date (see also Temperature) 65-70 requirements of date palm, discussion 58-70 History of date cultivation, remarks 17 150 THE DATE PALM. Page. Honey, date, production and use 30 Humidity, atmospheric, and rain, effect 011 date palm 52-58 exceptionally low in Sahara 70 Hybridizing, plant breeding, remarks 24, 98, 125 Ibn-el-Fasel, Andalusian Moor, note 72 Imperial soils, Salton, Cal., value for date 107-110 Importation of date palms and dates 35, 41, 132 Indians, Coahuila, tradition as to Salton Basin 103 Irrigation, areas of promise in Colorado River Valley 130 date, amount and application of water in United States 46 growing without use 131 in alkali desert, Algeria 78-80 palm, discussion 44-50 use of drainage water 98 with alkaline water, note * 50 earlier ripening of date by use of warm water 67 lack of water in Death Valley 123 of date lands in Salton Basin, notes , 108, 110 Salton Basin, history and progress 104 water for dates, advantages of warmth 49-50 Iteema date, note 37 Juice of date, draining off and preservation 30 Jus, M., estimate of water necessary for date palm 44 Kales date, note 128 Khadrawi date, note 38 Khalas date, quality, description, etc 36-37 Leaves, date palm, description, habit of growth 15 toughness and resistance to wind 71 use as shade 13 Life history investigations, importance in new crops, notes 139, 140 Loam soil, use for dates, notes 107, 108 Loozee date, note 26 LountNo. 6, date, notes 32, 128 Magnesium chlorid, preponderance in Ourlana (see also Alkali) 94 sulphate, high content in soil at M'rai'er, Algeria 89 Maktumdate, notes 39, 40 Male date palm, characteristic differences from female 25 pollination, chief requisite 24 palms, varieties, remarks 24 trees, proportion in planting 23 flower of date, differences from female flower 19 flower cluster of date, description , 26 Maquata Basin, Mexico, date growing, advantages 103, 135 Market and prices in United States for Deglet Noor dates 34 for dates in United States, extent .' 138 Maskat, exports of dates, notes 38, 41 Masselot, F., publications, references 26, 36 Maturity. See Ripening. McClatchie, Prof. A. J., notes on date culture 129 Means, Thomas H. , analyses of date soils Menakher date, quality, and need for trial in United States ' ' Merd el Ghram ' ' disease of date palm due to overirrigation 120 Mexican competition in date culture, improbability 134-136 Mexico, date culture, packing and production 41, 135 region, probable 103 insufficiency of heat for seedling dates, note •. male date palms, character and number, notes 20-23 "Meznoon" or "boussaafa" disease of dates 116 Mirhage date, notes 39, 40 Mohave Desert, date culture, chances of success 123 Moors, introduction of date growing into Spain 17 Moorzook, Fezzan, Sahara, effect of rain on date 118 INDEX. 151 Page. Morocco, excellence of dates, remarks 39, 40 Mozaty or Mazauty date, note 37 M'rai'er, Algeria, alkali in relation to date culture 88 Mulch, use in propagation of date, note 22 M'Zab, Algeria, dates 37 Nevada, date culture, probable success 125-126 kind of date required 33 New Mexico, date culture, probable success 133 Nice, date palm, ripening of fruit, notes 124, 125 Nitrate in Salton Basin soil, value and use 114 Nubia, dates of promise for United States 40 Offshoots, date, packing, and shipment, innovation by writer 42 loss of seedling date varieties by too close trimming 25 propagation of date palm 20 reproduction of date palm 15 Olive trees, protection of date palm 43-44 Orange orchards, Riverside, Cal. , injury by alkaline waters 121 Orchards, date, scientific starting (see also Offshoots, Propagation, etc. ) 25 seedling date, advisability of planting in Salton Basin 18 Oued Rirh, Algeria, date culture, remarks 89-90 Ourlana, Algeria, alkali in relation to date culture 89-95 Packing, gathering, curing of dates 29-30, 33, 137 offshoots (young date plants) for shipment, innovation by writer ... 42 Palgrave, W. G., remarks on Khalas date 36 Palm. See Date palm. Pangh Ghur region in Baluchistan, dates 1 . 37 Persia, dates of promise for United States 40, 126, 134 Persian Gulf, date, damage by •" shamel" wind 71 region, soil 109 dates, imports into United States, note 132 packing 137 tidal irrigation 48 oases, possible source for dates useful in Nevada and Texas 126 Phoenix canariensis, possible use in hybridizing date 125 reclinata (?) native growth and use in hybridizing 98 Phosphoric acid of Colorado River water, benefit to Salton Basin soil 106 Pit. See Seed. Plant breeding, hybridizing, remarks 24, 98, 125 Plant introduction, early maturing dates 133, 139 Planting and care of date palm offshoots 21 of date orchard, distances between trees 22 number to acre in desert, notes 45 proportion of male trees 23 seed, remarks 18 Plateau region, California, date culture, chances of success 123 Pollen of date, effect of character on fruit 24 shipment 29 Pollination, importance of labor, and ease for young trees 29 need of simplification of method 28 of date, difficulties 27,28 palm, discussion 26-29 dates, origin and practice 16 supply of male trees 23, 24 practice of Arabs in keeping pollen 28 value of Dakar majahel, male date palm, at Tempe, Ariz 24 Pomology, Division, early importation of date palms 41 Potassium chlorid in Salton Basin soil, value 1 14 Prices of dates, remarks '. 136-138 Profits of date culture 136-138 Propagation of date palm by offshoots -. 20 . seedlings 18 discussion 18-25 . proportion of male trees in plantations 23 dates, failure of seedlings in trueness to type 19 Pruning of date palm, trimming off of leaves 15, 25 152 THE DATE PALM. Rain and atmospheric humidity, effects on date palm, discussion ............ 52-58 at Moorzook, Fezzan, Sahara, destruction of date ....... . ........... _. . 118 in Death Valley, lack ................................................ 123 injury to flowers and fruit of date palm ................... ............ 54 notes on amount at various date-growing points ...................... 57 Rainfall, sufficiency, for dates in parts of California and Arizona (see also Rain ) 49 Rainy days and rainless months in date regions, records . ................... 56 Reproduction of date palm in natural state ................................. 15 Rhars date, good qualities ........ « ....................................... 32, 33 notes ................................................. 30, 41, 50, 132 Rohlfs, Gerhard, remark regarding dates in Morocco ......... . .............. 39 Ripening of dates, artificial, method ....................................... 135 benefit of hot dry wind ................................. 71 hastening by use of warm water in irrigation ............. 67 heat requirement ....................................... 65-70 Deglet Noor date, remarks ................................. 67, 68, 69 Rirh River. See Oued Rirh. Rolland, M. , estimate of water supply for date _____ ......................... 45 Roots of date palm, characteristics ......................................... 19 depth in alkali soil .................................... 112 moisture in earth, necessity ............................ 46 need of aeration . ...................................... 50 offshoots starting after planting ........................ 21 trimming in transplanting ............................. 20 fan palm in alkali, remarks ..................................... 112, 119 Rose, M. le commandant, estimate of water supply for date .................. 45 Sacramento and San Joaquin valleys, date culture, probable success ......... 123 Sahara, comparison of water supply with Colorado River ................... 105 dates and date palms .......................................... 39, 40, 41 importance of date growing .............................. ......... 17 investigation of alkali-resisting power of date palm .................. 73-99 protection of fig and olive by date palms ........................... 44 ratio of male date palms, note ..................................... 23 season of flowering of date ........................................ 27 Souf country, growing of Deglet Noor dates ........................ 35 sunken date gardens, description ..................... 69 study of alkali resistance of date palm ........................... 115-120 temperature curves in date region. . ................................ 63-64 temperatures, mean and mean maximum ........................... 66-68 Saharan alfalfa, use on alkaline soils in date orchard ........................ 23 varieties of date palms, introduction into United States ............. 41-43 Salt River Valley, Ariz., alkali in relation to date culture (see also Arizona) . . 99-101 climatic conditions for date .................... 53, 55, 57 date culture, probable success ..................... 127 irrigation water, temperature and -composition ---- i 49, 99 seedling dates ........................... ....... 32, 128 Saltbush, Australian, resistance to alkali ........................... I ..... 115, 121 Saltoii Basin, Cal. , alkali as compared with Algeria ........................ 93, 113 character ...................................... '. . 101 conditions in relation to date culture ........ ---- 101-114 amount of water needed for irrigation of date, note ....... 46 artesian wells .......................................... Ill chemical composition of alkali ................ , ....... 112-1 13 climate, remarks ............................... - ....... 112 culture of Deglet Noor dates .............. 33, 65, 67, 69, 110, 136 crop growing by Indians in early days ...... . . ........... 103 danger, possible, to date from cold ...................... 72 date culture advantages, summary ....................... 141 probable success . .......... ..'. 5, 12, 33, 67, 122, 136 growing areas .................. - .................. 110 dates to be secured ..................................... distribution of alkali, by depths ....................... 117-118 drainage for date growing, remarks ..................... 51-52 experimental garden at Mecca .......................... 110 fan-palm oases ......................................... HI fertility of soil ...................... r .................. 114 INDEX. 153 Page. Salton Basin, Cal., geography and geology 101 irrigation and water supply 12, 104 name, use 12 need of late sorts of dates, note 43 opening for date culture 33 Palm Canyon, comparison of soil with Sahara 112 profits of date culture, estimates 136 record of rainless months 56 region, promising, for date 67, 122 seedling date orchards, advisability of planting 18 similarity of conditions to Fougala, Algeria 83 to M'rai'er and Oued Birh regions, Sahara 88, 111 sum of mean maximum temperatures. < 68 mean temperatures 66 temperature curves. 63-64 treatment of alkali land in date culture 47 variation in temperature 59, 60 warmth of water for irrigation of dates 50 winter cold greatest danger to date 60 San Diego, date, failure to ripen 125 Joaquin and Sacramento valleys, date culture, probable success 123 Sandy soil, usefulness for dates, notes 107, 108 Sayer date, note Schweinfurth, Dr. Georg, claim as to influence of male date on seed Season for setting out date palm offshoots ^ 21 of flowering (bloom) of date 16, 27, 54 male date palm, relation to pollination 23 Secretary of Agriculture, inauguration of date study and introductory plantings 41 Seed and Plant Introduction anjd Distribution, Office, aid in study of date 41 of date, peculiarties of germination 19 Seedling date palms, growing near Yuma, Ariz 131 management in nursery, suggestions 19 dates, failure of reproduction true to type, note 19 in Arizona 32,128 of Mexico, probable value in United States 136 palms in propagation of date, discussion 18-20 Seeds of date, Deglet Noor, notes 33 importance to value of fruit 28 varietal characteristics 24 Seewahdate, note 32,61,129 oasis, origin of wahi date, note Seidell, Atherton, analysis of Sahara soils for alkali 73 Setting out date palm. See Planting. Sex of date palm, determination 29 "Shamel," hot wind of Persian Gulf, damage to dates 71 Shelter, for other fruit trees, value of date palm 43 Shipment of date palm offshoots, success 20-21 Simoons, effect on date palm 70-71 Sirocco, effect on date palm 70-71 Sodium sulphate, relations in soil water in Sahara 74 "Softdates," description 30 Soil conditions in Salton Basin, discussion 106-111 moisture, means of determining in study for date palm 75 reaction in relation to date culture ~ 119 samples near Palm Spring, Cal. , analysis Ill Soils, Bureau, relation to date growing of researches in Salton Basin, Cal 12 study of soils of Sahara for alkali, cooperation 73 of Sahara, investigation of alkali in relation to date culture 73-99 Salton Basin, analyses; fertility 113, 114 results of analyses at ten Saharan stations 96 Tempe, Ariz., analyses '. 100 used in date raising on Persian Gulf 109 water content in relation to alkali 75 Spain, introduction of date growing 17 Springs and wells, irrigation of dates in alkali deserts, Algeria 78-80 Subsoil, alkali, importance in date growing 116 Suckers. See Offshoots. 154 THE DATE PALM. Page. Sulphates, in Sahara in soils, notes (see also Analyses) 73, 87 Salton Basin soil, showing of analyses 112, 113 soil in Arizona, as shown in analyses ".. 100 resistance of date palm 87, 119 Sultani date, note 40 Summers, hot, necessity for date culture 63-65 Sunshine, necessity for date palm 58 Table dates, remarks .. 30 Tafi let, Morocco, excellence of dates, note 39 Taylor, Col. Sam., experiments with seedling date trees 20 Teddala date, notes 32, 33, 37, 132 Tedmama date, note 32 Tempe, Ariz. See Arizona. Temperature curves for date regions 63 heat requirements of date palm 58-70 high, necessity for fruiting of date 62 inversion by cold-air drainage, relation to date culture 61 limits of cold for date palms of varying age 60 low, cold-air drainage, cause of injury to date 61 endurance by date palm 59-60 mean annual range in several date regions 59 relation to growth of date fruit 52 Temperatures, sums for date season at various desert stations 66, 68 Tennessin date, note 32 Texas, kind of date required 33, 61 southwestern, date culture, probable success 134 Thermometer, need of device for finding date needs exactly 67 Thinning date bunches on tree, remarks 28 Tidal irrigation of dates, remarks 48 Timjooert date, notes 32, 37 Tourney, Prof. James W. , study of date in Arizona 41, 127 Trimming. See Pruning. Tunis, dates, suitable varieties for use in United States 133 male date palm for late pollination 24 United States, dates suitable for culture, discussion 30-44 importation of dates 14, 138 introduction of Persian Gulf and Saharan varieties of dates 41-43 names and notes on dates of promise 39, 40 regions of probable success of date culture 122-125 southwestern, importance of hardy dates 61 varieties of dates to be secured 38 Wahi date, origin, quality, description 39 Warm irrigation water for dates, advantages, discussion 49-50 Water, alkaline, use for date palms 44, 52, 121 amount needed for date palm, discussion 44-49 artesian, irrigation of date palm 82, 84, 90 Colorado Kiver, use for dates; composition 50, 105 drainage, use in irrigation of date palm 98 Salt River, composition 99 warm, advantage for irrigation of date palm 49-50 Weather, California, relation to date culture (see also Climate) 122-125 rainy, disastrous effect on flowers and fruit of date 54 Weevils, attacks on dates 31,39 Wells and springs, irrigation of dates in alkali desert, Algeria 78-80 Wheeler, Prof. H. L., experiments as to soil reaction, note 120 Whitney, Prof. Milton, attention to analyses of date soils 11, 73, 111 devising of instrument for determining soil moisture 75 Wind, effects-on date palm, discussion 70-72 pollination of date palm in wild state 26 Winds, cold, effect on date culture in Algeria and Persia 71-72 prevention of date culture on California coast 124, 125 Salton Basin, protection by mountains 101-103 sea, effect on date ripening in Mexico 135 INDEX. 155 Page. Winter, resistance of date palm to cold 59-60 Wolfskil 1 date, failure in reproduction by seedlings 20 notes 31,49,63,124 Yield of date palms in pounds, and continuance of bearing 26 dates, remarks 136-138 sunken gardens, and value of trees 70 Deglet Noor date 35 Hamraya date 37 Yuma, Arizona. See also Arizona arid Salton Basin. advantages for irrigation 87 date culture, conditions 131 9 Zab, Western, date region in Sahara, description, etc 78 Zero point for date culture 63-64 o [Continued from pain- '2 of cover.] No. 21. List of American Varieties of Vegetables for flu- Years 1901 and 1902. 1903. Price. 35 cents. 22. Injurious Kffects of Premature Pollination. IDOL*. Price, 11) cents. 23. Berseem: The Great Forage and Soiling Crop of the Nile Valley. 1902. Price, 1") cents. 24. The Manufacture and Preservation of I'nfermented ({rape Must. 1902. Price, 10 cents. 25. Miscellaneous Papers: I. The Seeds of Rescue < irass and ( Miess. II. Saragolla Wheat. HI. Plant Introduction Notes from South Africa. IV. Congres- sional Seed and Plant Distribution Circulars, 1902-190:5. 190:5. Price, 15 cents. 26. Spanish Almonds and Their Introduction into America. 1902. Price, 15 cents. 27. Letters on Agriculture in the West Indies, Spain, and the Orient. 1902. Price, 15 fenls. 28. 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