CACTI 



19 



flowers like other plants, it is true, but much more abundantly from 

 the cushions on the stems. This secretion is so abundant that it 

 dries into a globule of clear crystalline sugar on each pulvinus or 

 cushion wherever there are no summer rains to wash it off. 



The woody system is as variable as the plants themselves. It may 

 be made up of a cylinder of woody strands, or a mesh, or lacework, 

 with the modified buds at the intersections of the strands. 



The fruits are of great interest. They are more clearly modified 

 stems than those of almost any other plant. They bear rudimentary 

 leaves and cushions of spines like the stems. They may be sessile 

 on the plant or actually sunken into its tissues. They may mature 



Figure 1. — Two contiguous cushions on the edge and side of a joint of prickly pear : 

 a, Spines ; b, bristles ; c, spicules ; d, wool. The bristles differ from both spines 

 and spicules and are sometimes referred to as fugacious spines 



at the end of the season, or they may remain attached to the plants 

 indefinitely. They are usually single, but commonly proliferate into 

 a large pendent cluster which remains perennially attached. 



ATTRACTIVE INVESTIGATIONS WITH CACTUS SUBJECTS 



Very little attention has been given to the breeding of cacti other 

 than the genus Opuntia. Doubtless it is here that the quickest and 

 most profitable results are to be obtained. But what can be accom- 

 plished in other groups has not been studied much. 



The prickly pears are, however, very plastic, and variable hybrids 

 are easily obtained. It has occurred to the writers that an investi- 

 gator so situated that he can devote a liberal space to their culture 

 might bring together some very instructive data from the study of 

 a large number of crosses of these easily modified plants. 



