358 BOTANICAL GAZETTE [APRIL 
of the normal, no. 34, and while it is lower than that recorded for 
no. 22, it must be remembered that the high figure for total hydro- 
lyzable carbohydrates in no. 22 is due in a large measure to the high 
concentration in the pulp of soluble non-reducing sugars, the term 
“total hydrolyzable carbohydrates,” as defined, covering hydrolyz- 
able carbohydrates of all types, soluble and insoluble. On the 
other hand, we know that the insoluble polysaccharides of this type 
do break down in the course of long confinement without photo- 
synthesis; witness the difference in the figures for total hydrolyzable 
carbohydrate in the case of the normal, no. 34, and no. 7, which 
rested in diffuse light more than 6 years. Much of the polysaccha- 
ride content of no. 7 has evidently disappeared in the course of its 
starvation; yet what happened to no. 7 in 6 years in diffuse light 
has not happened to no. 23 in 22 monthsin darkness. The breaking 
up of the stored insoluble polysaccharides in response to the plant’s 
demands on its source of energy evidently takes place very slowly, 
and this fact, taken in conjunction with that of the resistance of the 
Echinocacti to desiccation, helps in a large measure to explain the 
viability of these plants in spite of prolonged starvation. 
Desert LABORATORY 
Tucson, Ariz. 
