CACTE.E 7 



occur, having only one cotyledon, while one of them in other 

 cases is bifid. Other species of Opuntia observed not only 

 differ from most members of the Order, but also remarkably 

 from the last species mentioned. The hypocotyl of 0. 

 Labouretiana is subterranean, and the cotyledons are ovate, 

 obtuse, fleshy, and very unequal, the larger one being about 

 2 cm. long, and 1-5 cm. wide, and the shorter one 1-5 cm. 

 long, and 1 cm. wide. They are deep green and persistent. 

 Those of 0. occidentalis (fig. 400) are similar, but smaller in 

 every way. In both of these species true leaves occur a 

 very unusual occurrence in the Order. They are small, subu- 

 late, succulent, seated on little elevations of the stem, 

 surrounded by fascicles of spines and arranged in ascending 

 spiral rows ; but as they become yellow and fall away early, 

 they are comparatively functionless. Large foliaceous and 

 persistent leaves occur in the species of Pereskia. The 

 cotyledons of Phyllocactus stenopetalus (fig. 397) are similar 

 to those of Opuntia occidentalis and 0. Labouretiana ; but are 

 very much larger. The hypocotyl is terete and unusually 

 elongated, while the stem is much flattened and leafless, with 

 fascicles of short bristles at the nodes along the edges. The 

 genus Nopalea is closely allied to Opuntia, and N. dejecta 

 resembles Opuntia basilaris in its hypocotyl, which is cylin- 

 drical and 1-6 cm. long ; but the large ovate fleshy cotyledons, 

 the conical fleshy stem, and the small caducous leaves resemble 

 those of Opuntia Labourtiana. 



Mamillaria Goodrichii, Scheer. 



Primary root small, tapering, with very few lateral rootlets, but 

 numerous root-hairs. 



Hypocotyl succulent, ovoid at first and afterwards globose, 

 glabrous, pale transparent green, suffused with pale purple, 2'5 mm. 

 long, 3'75 mm. broad. 



Cotyledons represented by the margins of a cleft at the apex of 

 the hypocotyl, and soon becoming indiscernible. 



Stem succulent, developing very slowly and crowned in the 

 seedling stage with tufts of short slender spines ; spines pink, ulti- 

 mately white, pubescent, about equal in size. 



Leaves none or represented by the above-mentioned spines or 

 bristles. 



