116 THE DATE PALM. 



4 per cent of their weight of alkali, it does not produce fruit unless its 

 roots reach a stratum of soil where the alkali content is below 1 per 

 cent, and does not yield regular and abundant crops unless there are 

 layers in the soil with less than 0.6 per cent of alkali. The surface 

 soil may, however, be very much more salty, and may even be covered 

 with a thick crust of alkali. It is probable that amounts of alkali 

 below 0.5 per cent of the weight of the soil exert no appreciable 

 injurious influence on the date palm. For example, in a flourishing date 

 plantation at Ourlana, in the Algerian Sahara, at the spot shown in Plate 

 XVII, figure 1 (Ourlana, station No. 2), the surface foot of soil contained 

 no less than 1.52 per cent of alkali and was covered with a crust, while 

 the subsoil at 2 to 3 feet showed only 0.51 per cent of alkali. The 

 water used to irrigate this soil contained 0.64 per cent of soluble salts, 

 of which 0.40 per cent consisted of injurious alkali. Both in the soil 

 and in the irrigation water the chlorids, very harmful to most plants, 

 predominated; they constituted 80 per cent of the alkali in the sur- 

 face soil, 40 per cent in the subsoil, and 52 per cent of the dissolved 

 salts in the water. These amounts of alkali of so harmful a character, 

 though sufficient to prevent the culture of any ordinary crop, seemed 

 to be entirely without influence on the growth or yield of the date 

 palm. 



If the soil at all depths contains somewhat more than 0.6 per cent of 

 alkali the growth is slower and the yield less than in better land, and 

 where the alkali content is everywhere over 1 per cent date palms 

 do not bear fruit regularly and their growth is very slow. On trees 

 growing in the presence of very large amounts of alkali the leafstalks 

 are usually of a pronounced yellowish color instead of the normal gray 

 green; on such soils in the Sahara the only other vegetation that can 

 exist is a scanty growth of samphires and saltbushes. (See PL XV, figs. 

 1 and 2.) 



It must be borne in mind that the percentages given above are for 

 the stratum of soil containing the least amount of alkali and that the 

 surface layers may contain very much more, since the date palm has 



A diseased condition of the date palms called at Fougala, Algeria, "meznoon" (zas 

 in azure), meaning " crazy," occurs rather often among the trees growing on the 

 , worst alkali spots and maybe caused in some way by the presence of excessive 

 amounts of saline matters in the soil. The leaves of such' palms do not unfold prop- 

 erly, but remain dwarfed and distorted, as is shown in Plate XV, figure 2. (This 

 figure shows in the foreground the samphires and saltbushes characteristic of the 

 most alkaline soils. ) These meznoon palms are said to be cured in some cases by 

 cutting off all the young leaves and hollowing out the bud, as is done in making 

 ' ' lagmi ' ' or palm wine. When the new leaves push out some months later they 

 are sometimes normal. The Arabs sometimes attempt to cure such trees by tying the 

 youngest leaves into a compact bundle. A somewhat similar disease is described by 

 Masselot (Bui. Direc. Agricult. et Comm., Tunis, vol. 6 (1901), No. 19, p. 134) as 

 occurring in the Tunisian Sahara, where it is called "boussaafa." It attacks princi- 

 pally young palms and by preference the Deglet Noor variety. 



