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. 



