MINIATURE FORTRESSES 121 



stem or trunk, from which branch many grotesque, weird- 

 looking arms and legs that cause the whole plant to resemble 

 a dwarf tree though it is typically shrubby in habit. A few 

 of these fantastic forms have the joints club-shaped, some- 

 times quite slender, and these types are intermediate be- 

 tween the Prickly Pears and the Cholla, growing mostly as 

 prostrate shrubs rather than as dwarfed trees. Prickly 

 Pears and Cane Cacti alike have only one kind of spines in 

 the areolas, though these are usually of several lengths, and 

 both bear spicules along with their thorns. In the Cholla the 

 tubercles are arranged spirally on the cylindrical joints, each 

 bearing an areola which in turn has the spines and spicules 

 and also the small, greatly reduced fleshy leaves half an Inch 

 long or longer ; these always wither and fall off in a few days, 

 showing no doubt that they are but remnants from an earlier 

 age, when possibly the prehistoric cactus bore much larger 

 leaves. Cholla thorns have very thin and transparent 

 sheaths, which persist unless destroyed or rubbed off, thus 

 differing from Prickly Pear thorns. Cholla spines are not 

 messengers of harmony, nor do they welcome the tenderfoot 

 tourist in his journey across the desert, for sheathed Cholla 

 thorns constitute the most treacherous and dangerous of the 

 cactus spines, a formidable fortress of strong, sharp, dan- 

 gerously recurved spikes; and woe to the careless stranger 

 who is inadvertently stabbed by one of these terrible Cholla 

 swords ! 



We have noted that the Prickly Pear blooms open in the 

 early morning, closing in late afternoon with one or two ex- 

 ceptions. Among the very unusual Cane Cacti the opening 

 of the flowers seems to be on a sort of schedule, for we ob- 

 serve that they unfold at different times, as at eight o'clock in 

 the morning, at nine, at ten, at one o'clock, at three, and at 

 four, then all close in the evening usually never to open 

 again. So if you are to see this phenomenon you will have 



