CACTACE^ OF MEXICO SAFFOKD. 



539 



in the markets of Mexico under the name of " raiz de nopal," for use 

 in setting broken bones, the drug venders declaring that it will cause 

 the bones to knit speedily. 



LEA^^;S AND AREOLES. 



All cacti have leaves, though 

 in some species they are rudi- 

 mentary, or rather vestigial, 

 and so small that they can not 

 be seen with the naked eye. In 

 others they are large and per- 

 fectly developed, either with 

 petioles and feather veins, as 

 in Pereslda aculeata (fig. 10, p. 

 545), sessile and flesh}'-, with 

 only the mid nerve or several 

 parallel nerves indicated, as in 

 certain species of Pereskiopsis 



Fig. 3. — Opuntia joint, with leaves. 



(pi. 10, fig. 2), or cylindrical, or awl-shaped and caducous, as in the 

 genera Opuntia and Xopalea. In the axils of the leaves are situated 



the areoles. These are little cush- 

 ions clothed with down or felt-like 

 wool from which the spines issue, 

 and in some genera the flowers 

 also. In Opuntia and Pereskiopsis, 

 in addition to the spines, they 

 usually bear a tuft of small, short, 

 barbed bristles, called glochides or 

 glochidia. 



SPINES. 



The spines are not connected 

 with the woody axis of the stem 

 or branches, but emerge from the 

 areoles, as indicated above. In 

 some species they are simple and 

 straight, either bristle like, awl- 

 shaped, or short and conical. In 

 others they are bent like fishhooks 

 or curved and horn-like, with trans- 

 verse ribs (pi. 13, fig. G). Some- 

 times they are minutely pubescent 



or hairy and sometimes even plumose or feathery (pi. 3, fig. 6). 



They may be grouped in star-like clusters, with straight or curved 



Fig. 4. — Cactus spines. 



