184 



The Journal of Heredity 



L. C.C. KriEOER 



A WIDE RANGE OF VARIATION 



A single pulvinus or cushion of spines from each of five varieties of the prickly pear known 

 to botanists as Optinlia cacanapa. The long stiff spines vary in number frorn to 9. It 

 is not difficult to breed most of the spines out of a variety of prickly pear, but it is much more 

 difficult to eliminate the short, tender spicules which cluster around the base of the spine. 

 Most varieties of "spineless cactus" lack spines but still possess a certain number of 

 spicules; this makes them unpleasant to handle but does not absolutely prevent their use 

 as stock feed, since cattle can handle quite rough feed. Illustrations about one-half 

 natural size. (Fig. 15.) 



turned out as well as was expected when 

 they were found. Forms of Opuntia 

 dillei were once looked upon as promis- 

 ing; but these have long since been 

 proved of no value — at least so far as 

 three or four forms which we ha\'e 

 carefully studied are concerned. In 



all of these in\-estigations, the desire 

 has been to secure as a starting point 

 for hybridizations the least spiny plants 

 possible consistent with a reasonable 

 expectation of rapid growth. Out of 

 3000 forms collected only three, with a 

 possible additional two more, are now 



