EPHEDRA ANTISYPHILITICA. 15 



nated from the groups of deciduous rootlets of the host, at whose base the 

 attachment took place and penetration occurred. 



The anatomical relations of host and parasite were not studied in detail, 

 but the union of the two species is shown by fig-. 3, plate 4, and it is seen 

 that the general form of the sinker recalls that in Covillea; that is, it is 

 blunt, and not wedge-shaped as in some other plants. Thin-walled cells, 

 of the epithelial type, bound the haustorium both in the cortex and in the 

 woody cylinder of the host, into which the haustorium had penetrated a 

 short distance. 



From the character of the haustorium and its relation to the host, and 

 from the large number of attachments, it must be concluded that the par- 

 asitism of Krameria on Encelia is very deleterious to the latter. 



Ephedra Antisyphilitica. 



In the vicinity of the Desert Laboratory Ephedra is closely confined in 

 its distribution to localities where there is a considerable depth of soil, and 

 consequently where the moisture content throughout the year is relatively 

 high. Near the specimen studied were growing Acacia constricta, Covillea 

 tridentata, Lycium andersonii, Parkinsonia torreyana, Prosopis velutina, Zizy- 

 p/ms parryi, and other trees and shrubs. 



The root-system of Ephedra is characterized by a stout tap-root and few 

 and relatively slender laterals. The main root was 13 cm. in diameter at 

 the crown and was traced directly down 75 cm., where it forked, one 

 branch of which, after running a few centimeters horizontally, turned 

 downwards and attained a depth of over 1 meter. The laterals took their 

 origin from 15 to 50 cm. beneath the surface of the ground and (as is 

 usual in the desert plants where adequate soil -space is to be had) either 

 went directly outward or directly down soon after leaving the central axis. 

 A lateral which arose 15 cm. beneath the surface ran outward, maintaining 

 the same depth with much consistency, until the tip was 1.8 meters away 

 from the main root. Most of the laterals, however, were more deeply 

 placed than this one. 



Parasitism of Krameria on Ephedra was seen on the more superficial 

 roots and larger roots only. The frequency of attachments on the host 

 root is shown by the fact that on one (which was 1 cm. in diameter) 6 

 haustoria were counted within a space of 15 cm. 



The root of Ephedra is characterized by large ducts, considerable wood 

 parenchyma, and few and very broad medullary rays, which at the peri- 

 phery of the wood cylinder may be 8 cells in thickness. In a root 1 cm. 

 or less in diameter the medullary rays are narrowly wedge-shaped in cross- 

 section. 



The form of haustoria in Ephedra is apparently conditioned by the char- 

 acter of the medullary rays. In a transverse section of the host root, one 



