CACTUS SPINES AND PECULIARITIES 29 



doubtless much faster now than formerly, and in future we 

 shall have many additional instances to record, as it is quite 

 likely that new species are originating under experimentation 

 through careful selection and ingenious plant breeding. 



SPINES AND FLOWERS 



The spines of cacti are ever an interesting subject for 

 study, and the very name "cactus" is suggestive of thorns. 

 It is generally known that cactus spines develop from their 

 bases and that they are impregnated with resin or a resinlike 

 substance, while the spines of nearly all other plants (as for 

 instance the plum) grow from their tips and are not resinous 

 in character. A young growing cactus spine has a very soft 

 yielding base while the tip is hard and sharp, and the sides 

 retrorsely barbed. Because of their resinous nature the 

 thorns persist on the desert long after the cactus body has 

 disappeared, and often fragments of the thick cuticle remain 

 with them, still firm, sharp and translucent. Such spines 

 about a spot where a noble Sahuaro or Giant Cactus has 

 fallen and gone back to Nature as dust may persist for a long 

 period unchanged, without crumbling or otherwise disin- 

 tegrating; this is true also of those of the bisnaga or barrel 

 cactus. Thorns grow on the Giant Cacti for a hundred, 

 even two hundred years, unalterable, sharp and hard and 

 dangerous. Some species of cactus have as many as three 

 kinds of spines: centrals, the inner thorns, usually the largest 

 and stoutest; radials, the outer spines; and what are termed 

 "bristles" but are more accurately described as "antennalike" 

 spines. In some groups, as the bisnaga, the spines are cross- 

 ridged or marked transversely, with the tips smooth, straight, 

 or hooked. Many cactus spines are marked with brilliant 

 colorings, and some are transversely banded with bright 

 variegated "zones" of color. When held to the light they 



