256 BOTANICAL GAZETTE [OCTOBER 
The Opuntia versicolor which had been fastened in a cavity in 
the side of a tall Carnegiea early in 1909, lost three of its four 
short branches and the terminal section of the stem during the 
dry foresummer of 1910. Activity in the rainy season in the 
midsummer following resulted, not in the formation of additional 
sections or members, but in the increase in thickness of the stem 
FIG. 3.—Opuntia versicolor parasitic on Carnegiea gigantea, March 1910 
and roots; the latter were thin and fibrous when the preparation 
was made, January 23, 1909. After two years of parasitic exist- 
ence, the visible portions of the root system were much enlarged, 
after a manner sometimes exhibited by autophytic individuals 
of the same species (figs. 3 and 4). 
An Opuntia Blakeana set in a cavity of Carnegiea, where it 
was held by plaster, early in 1909, likewise formed no additional 
