186 



The Journal of Heredity 



i'T fit 







A COMPLETELY SPINELESS CULTIVATION 



Two-year-old plant of Opimtia siiharmala, a native of Southern Texas and a result of selection 

 in the work of the U. S. Department of Agriculture to produce hardier varieties of spine- 

 less cactus for the Southwest. This plant is perfectly spineless, and the number of spicules 

 is not large. This species will stand from 12° to 20° more cold than the commercial vari- 

 eties of spineless cactus at present known, which are too tender to be grown except under 

 most favorable conditions. (Fig. 17.) 



tions from this arc now entirely destitute 

 of spines. The latter form is described 

 beyond; but it will be instructive at 

 this point to glance briefly at some of 

 the diversities which are encountered 

 in this species — or no doubt some one 

 will say "group of species;" for we 

 have here either one species, or we have 

 more than one. The important fact, 

 though, from our standpoint, is that 

 one form is nearly or quite spineless, 

 and remains so when propagated vege- 

 tativcly. 



MICH VARIATION FOUND. 



When this species or this group of 

 species is studied broadly, one finds 

 greater differences than constitute good 

 sjjccies elsewhere in the genus. There 

 is, however, a scarcely definable some- 

 thing that links the diff"erent forms 

 together unmistakal)ly. And this some- 

 thing is a quality that does not require 

 a trained botanist to recognize. Indeed, 

 the Mexican peon will point to all these 

 forms with unerring certainty as "caca- 



' A peculiar condition is found in one California species wlierein the variation occurs, not 

 between the individual ])lants but uj)on the joints of a single plant. This has not yet yielded to 

 selective influences. 



considered at all promising for this 

 jjurpose. These, we think, belong to 

 as many botanical species.^ 



As stated in a previous publication, 

 some of the species which are fed very 

 successfulh' in southern Texas are not 

 adapted at all for our purpose because 

 of being jjersistently spiny. However, 

 in one general region of Texas the native 

 species normally are very variable in 

 spination; and occasionally plants are 

 met with which are very nearly or 

 even quite destititte of spines. The 

 greatest variation the writer has ever 

 known in a single species of prickly 

 pear is exhibited in Opuntia cacanapa. 

 This species as conceived when it was 

 first described has one erect white or 

 bone-like sjjine to each arcolc or 

 cushion of s])ines. Further study has 

 proven that its sjjines may be three or 

 even six in number; and one jjlant of 

 "cacanapa" has been found, which is 

 nearly destitute of spines, and has even 

 the number of spicules somewhat re- 

 duced. \'egetatively ])ropagated selec- 



