300 



D. T. MacDOUGAL 



small woody legume were collected near Kharga which could not 

 be named. An herb probably a crucifer was also found out in 

 the desert to the westward of this place which was represented only 

 by dead stems, and capsules. This last-mentioned was the only 

 native plant the activity of which seemed to be conditioned by 

 precipitation. 



Two of this small list of plants habituated to desert conditions 

 were grasses, three were chenopods, two were crucifers, two were 

 legumes, one a tamarisk, one a smartweed and one a zygophyll. 

 The single parasite probably requires some time for attaining 

 maturity, but its cycle closes with flowering. But one, and that 

 an unrecognizable species, was an annual; the irregularity and 

 sparsity of the rainfall precluding anything like the development of 

 annuals to be found in the mountainous regions east of the Nile 

 or in the American deserts. 



Alhagi is very spinose, and Aristida has an armored effect, with 

 its pointed, rigid leaves; but the remainder of the species were 

 simply indurated and leathery, exhibiting but few of the structures 

 to which many writers ascribe a protective function. It is notable 

 that the most spinose member of the group is the favorite food of 

 the camel. No examinations of root systems were made. A root 

 system of sensational dimensions is attributed to Calligonum by 

 Volkens from a superficial examination of the upper part of the 

 underground organs. Cannon, however, in some excavations in 

 northern Algeria, concluded that the roots were mostly arranged 

 in generalized types of branching, diffusing in all directions from 

 the base of the stem. Nothing in the soil conditions would spe- 

 cially favor great extension of any member except, perhaps, cases 

 in which the ground water diffused upward through a narrow 

 crevice or chimney in a hard substratum. 



Tt is notable that succulents are not represented in the plants 

 mentioned above. The three chenopods are halophj^tic but did 

 not appear to have undergone hydration to such extent as to 

 permit the accumulation of any great surplus or balance of water. 

 Most of the fleshy halophytes of this family wilt very quickly when 

 the water supply is cut off, but these forms seemed capable of long 

 endurance to drought, and such capacity would be necessary for 

 their continued existence in this region. 



