DEPARTMENT OF BOTANICAL RESEARCH. 6l 



obtain comparative data, and then a return was made in March to Biskra for 

 the purpose of completing certain exact observations. 



The reduction and compilation of results has not yet been made, but the 

 following general characterization of the vegetation and surface conditions 

 may be presented at this time. It is to be noted that the region traversed 

 offered a surface covered chiefly with stones, comparatively little sand being 

 encountered. Gypsum is an important constituent of the soil, a hardpan is 

 present, and water may be found (at varying depths) 3 or 4 feet below the 

 surface at Ouargla, and over 400 feet below in the region of the "dayas" 

 south of Laghouat. At Ouargla the superficial water is heavily charged with 

 salts. The rainfall at Biskra averages about 9 inches annually and is con- 

 siderably more than in the region farther to the south. 



The region traversed is treeless, except in the "dayas" south of the Saharan 

 Atlas Mountains. The plains bear inconspicuous shrubs of such meager- 

 ness as to give very little character to the landscape, although as many as 

 400 individuals might be counted in an area of 50 square feet. Some peren- 

 nials bear small fleshy leaves, the roots of Citrullns are much thickened, and 

 a small Euphorbia, also with roots somewhat fleshy, is rather common; yet 

 distinct succulents or plants with a large water-balance are not components 

 of the flora. The horizontal and superficially disposed root-systems such as 

 are furnished by the cacti are not seen here and but few species have a 

 deeply penetrating tap-root. The greater number of plants have a diffused 

 or "generalized" root-system which, on the plain, penetrate to a depth of 

 3 feet or less, and in the oueds sometimes to 6 feet and possibly more. The 

 physical relations of plants to the soils promise some close adjustments, as 

 a number of species were seen at Ghardaia in November in leaf and flower, 

 although no rain had occurred for a year. 



Perhaps nowhere else in the world may such interesting results of the 

 attacks of grazing animals on vegetation be seen. The gazelle (Gazelle 

 dorcas) was doubtless very abundant in this region during the periods in 

 which it has not been occupied by man, and the species is frequently encoun- 

 tered at the present time. Southern Algeria has been inhabited by Arabs 

 for 800 years and large numbers of sheep, goats, and camels graze every- 

 thing very closely. Although the vegetation on certain protected areas is 

 more abundant than on the open plains, it is not certain that any species has 

 been exterminated, although the form, number, and distribution of the spe- 

 cies eaten has been greatly modified. 



The Water-relations of Halophytes and Sclerophylls, by Prof. F. E. Lloyd. 



Data were obtained for the determination of the absolute, relative, and 

 cuticular transpiration of such beach plants as Abronia latifolia, A. umbel- 

 lata, Cakile americana, and of trees and shrubs from neighboring slopes, 

 including Quercus agrifolia and Rhanimis purshiana. A method was de- 

 vised for observing the actual condition of stomata on living leaves by the 



