DATES OF EGYPT AND THE SUDAN. 15 



Algerian Deglet Noor trees from offshoots brought to Merowe were 

 shown to the writer by Gov. Jackson in first fruit, and in the latter 

 part of September the fruits were ripe and as hard as the dry dates 

 of the country. This same tendency to become dry or "mummified" 

 is observed in the Deglet Noor in the Coachella Valley in California 

 in exceptionally dry, hot seasons, especially if a minimum amount of 

 water is given them. 



The preponderance of dry dates in the Nubia and Sudan portions 

 of the Nile Valley may, then, be attributed to two general causes, 

 namely, the general tendency of the climate to the production of dry 

 varieties and the selection of such dry varieties as are of greatest 

 commercial value. Such selection is on account of the readiness 

 with which they are cured and the convenience with which they are 

 stored and transported, their indestructible character permitting their 

 being packed in stout bags and carried by camel caravans subject to 

 the hardest conditions, yet always ready as an article of food without 

 preparation. 



Referring to the temperature diagrams in figure 1 and the plotted 

 curves in figure 2, it will be seen that at Merowe and Khartum the 

 lowest monthly means, December and January, are considerably 

 above the line of 64.4° F., assumed to be the zero point of activity 

 of the date tree in flowering and fruiting functions. In spite, how- 

 ever, of the high December and January means, the date trees of 

 Dongola flower and are pollinated at about the usual time of dates 

 farther north. According to Davie, "pollination takes place in Feb- 

 ruary and March," practically the same months when it is practiced 

 in Dakhleh and Khargeh, where the means of December and January 

 are considerably below 64.4° F. That is, a continuous mean tem- 

 perature for those months of several degrees above the assumed zero 

 point does not prevent these trees from having a resting period and 

 postponing the flowering period to about the season when it occurs 

 in considerably cooler localities. Davie records that the fruit at 

 Merowe ripens about seven months after pollination, or September 

 and October, but at the time of the writer's visit to Merowe, on 

 September 20, nearly all the dates had been gathered, the Barakawi 

 harvesl bad ended practically a week previously, and much of the 

 fruit was being marketed. These facts point strongly to the necessity 

 of a study of date-tree activities from another standpoint than that 

 of a mean temperature of 64.4° F. as tho zero point. 1 



» Dr. A. I.. Vinson, of the Arizona Agricultural Experiment Station (in I'.otanieal (lazette, vol. 37, p. 

 324 27), d rate of leaf grow tli of two trees each of the Deglet Noor and Hilars varieties at the 



cooperative date garden, 1 empe, Ariz., through the grow log leasonsol 1008 and 1907 and calls attention to 

 the agreement of the rate oi growth wiih the mean mini mum rather than with the menu maximum tem- 

 odied. Sis diagrams are, however, too much Involved with the waning growth 

 efthesnecessive leaves as they approach maturitj to make hi .conclusions convincing, in fact, his growth 



curves show a more intimate coordination with the surface^.soil temperature than with any other factor. 



