KOOT-SVSTEMS OF PEREXXIAI.S. 



59 



Fig. 6. — Root-systems of Covillea Iridentaia, from various locations on the domain of tl:c 



Desert LaboratoO'. 

 I! and h. Horizontal extensions of root-system of one plant, separated for sake of cleanicss. 



Dotted lines indicate the intruding roots of neighboring Covilleas encoimtered on the 



same level, or nearly so, as the roots of the plant studied, 

 c. Vertical extension of bajada-grown plant. 

 d and e, Vertical extensions of root-systems of two plants from the flond-plain of West Wash, 



Entire length of laterals in c is not shown. 



About lo large and numerous small laterals were given off from the 

 main root within 15 cm. of the surface of the ground. These roots were 

 from 5 mm. to i.i cm. in diameter at the base, and the longest extended 

 as far as 4 meters from the central root axis. This, the longest lateral, 

 branched from the main root ;, cm. from the surface, and lay 2r, ;,9, ;,i, 

 and 28 cm. from the surface of the ground at various distances from its 

 base. The position of this root with relation to the surface is fairly illus- 

 trative of all of the rest. The mutual relations of the principal roots, 



