4 BULLETIN 271, U. S. DEPARTMENT OF AGRICULTURE. 
when taken in connection with a fruit as exacting In temperature 
requirements as the date it becomes of very great importance. 
Another important factor in the environment of the date tree is 
the relative humidity of the air, which along the Mediterranean coast, - 
where there is an extensive culture, is very high throughout the year. 
At Alexandria, with a record of 23 years, the mean monthly range of 
relative humidity is from 64 to 72 per cent, with an annual mean of 
68, some years running to 71 per cent. At Gizeh the mean relative 
humidity of a 10-year record is 69 per cent, with single monthly 
means as low as 50 and as high as 84 per cent. At Heluan the desert 
influences begin to be felt, and the mean relative humidity is reduced 
to 54 per cent, and at Siut (Assiut) it is 53 per cent. Aswan gives a 
record of 39 per cent humidity as a mean for 11 years, while the Oasis 
of Dakhleh, on a record of 7 years, shows real desert dryness, with a 
mean humidity of only 36 per cent, and Wadi Halfa, on a 20-year 
record, has the low mean of 34 per cent. ; 
No weather records are available for the Sukkot region, formerly so 
important, but now superseded in the volume of date production by 
Dongola Province. Merowe, the capital of Dongola, fortunately has 
- very complete records for recent years and shows the greatest dryness 
of any date region yet studied, its mean relative humidity for the year 
being only 24 per cent. For May, the driest month, the record is only 
12 per cent on a 5-year mean; 30 per cent in August and 31 per cent 
in January, the most humid months. 
Passing the fourth and fifth cataracts with considerable date culture 
in Berber Province, at the next weather station, Atbara Junction, 
influenced by the nearness of the rainy hill region on the east and 
southeast, the mean humidity rises to 38 per cent, reaching 50 per cent 
in August, with occasional records for April and May as low as 16 per 
cent. At Khartum, beyond which few date trees are found, the mean 
humidity for the year drops to 33 per cent. 
For convenience in studying the character of the dates produced as 
related to their environment, the region under consideration may be 
divided as follows: 
(1) The maritime subtropical: Comprising Lower Egypt, or the 
Nile delta, including lower Gizeh. 
(2) The desert subtropical: Comprising Upper Egypt to Aswan, 
with the Libyan oases. 
(3) The desert tropical: Comprising Upper Egypt beyond Aswan 
and the Nile Valley in the Sudan at Khartum. 
Hard and fast lines are difficult to draw, and if there were a greater 
number of observation stations it is probable that poimts on the mar- 
gin of the delta toward the desert, like Salihieh and Korain on the 
eastern border of the delta and Manshia to the west of Gizeh, would | 
show temperature and humidity conditions which would place them 
