THE NEW OPUNTIAS 



sometimes found, always growing, however, in 

 places absolutely inaccessible to browsing ani- 

 mals. In California, Mexico, Colorado, New 

 Mexico and Texas, small patches of half-thorn- 

 less ones are sometimes found, almost always 

 in inaccessible crevices among the rocks. On 

 some of the South Sea Islands, where vegeta- 

 tion is abundant and browsing animals few, 

 the opuntias, having no use for thorns, have 

 become hair -like, diminished and perfectly 

 harmless." 



From year to year, as the test has advanced, 

 Mr. Burbank has had occasion to draw upon 

 the following cacti, which, with others, have 

 formed the groundwork of this great experi- 

 ment, — the list will suggest something of its 

 scope, as well as its complexity: 



General varieties, — Albispina, arbuscula, ar- 

 borescens, basilaris, Bernadina, Brasiliensis, 

 camanchica, dearmatus, Emori, Englemanni, 

 formidablis, frutescens, fulgida (cholla) fragilis, 

 galopageana, gummosa, humifusa, kevis, lepto- 

 caulis, lurida, Missouriensis, monacantha, ma- 

 crorhiza, nigricans, papyracantha, phasnacantha, 

 Rafinesquii, senilis, spinosoir, triacantha, ursina, 

 and others. 



377 



