296 



BOTAMCAL GAZETTE 



[OCTOBER 



spines. Small awl-shaped leaves about 15 cm. in length are also 

 borne just below the spines in the spring, but are soon abscissed. 

 The plant grows in the most exposed situations. It was first 

 described as a new species by Rose (5) in 1909, and the plant 

 from which the type specimen was obtained furnished most of the 



Fig. i. — Etiolated shoots of Opuntia Blakeana sprouting from normal shoots 

 which had been removed from open environment to dark chamber. — Photograph by 

 D. T. MacDougal. 



norm 



used in this study. 



grown from 



been removed to the dark constant temperature chamber of the 



Laboratory 



Method 



The chamber in which the etiolated shoots were grown has 

 been fully described in publications of the Desert Laboratory, 



