546 ANNUAL REPORT SjMITHSONIAN INSTITUTION^ 1908. 



53, 54, 1909. According to Professor Pittier the fruit is eaten by 

 cattle during the dry season. The lens-shaped seeds have a glossy 

 testa, which serves to distinguish this genus from the somewhat simi- 

 lar Pereskio]3sis, in which the seeds are covered with matted hairs. 



II. SUBFAMILY OPUNTIOIDE^. 



This subfamily is distinguished by the leaf-like cotyledons of its 

 seeds ; its fleshy leaves, either broad and lasting, as in Pereskiopsis (pi. 

 10, fig. 2), or small, terete, and caducous, as in Opuntia and Nopalea ; 

 and by the barbed bristles, or glochidia, borne on the areoles, usually 

 small and very numerous and mixed with soft wool. These glochidia 

 are extremely sharp and barbed. They are loosely attached at their 

 insertion, so that they are loosened by the slightest touch and adhere 

 most annoyingly to the skin or clothing. In this subfamily the spine- 

 bearing and the flower-bearing areoles are united into one circular pul- 

 villus in the axil of the leaf. The spines occur in the lower and the 

 bristles in the upper part of the pulvillus. Between the glochidia and 

 surrounded by them, and always above the spines, the young shoot 

 or flower originates (pi. 10, fig. 6). These glochidia correspond with 

 the bristles and wool in the axils of some Eumamillaria and with the 

 tomentum of the floriferous areole in Coryphantha and Echinocac- 

 tus; but they are quite distinct morphologically from the spines 

 themselves. They continue to grow year after year, becoming longer 

 and more numerous, and in many species the spines themselves con- 

 tinue to grow and increase in number.'* 



1. Pereskiopsis. — This genus, with broad, fleshy leaves, needle- 

 like spines, glochidia, opuntia-like fruit, and seeds covered with 

 matted hairs, is represented in Mexico by several species. In the 

 vicinity of Guadalajara the fruit of Pereskiopsis aquosa (pi. 10, 

 fig. 2) is gathered for food and sold in the markets as "tunas de 

 agua." It has subspatulate-elliptical, sessile, acuminate leaves, which 

 are obscurely 5-nerved. The areoles, which are scantily provided 

 with wool, bear at length usually a single white or grayish spine 

 tipped with brown. The edible part of the fruit is the watery 

 endocarp, or rind, which has an agreeable odor and taste, somewhat 

 like that of an apple. The seeds are margined distinctly, with the mar- 

 gin prolonged into a kind of tail-like process extending over the 

 funiculus, or seed stalk, and are clothed witli cotton-like fiber. Conse- 

 quently they are quite different from the smooth, glossy, lens-shaped 

 seeds of Pereskia, and would alone serve to distinguish Pereskiopsis 

 from that genus. Another species from the same locality is Pereskiop- 

 sis calandrinicefolia^ with broad, spatulate leaves and prominent 

 cushions of felt on the areoles, from which several long, slender, 



'» Engelmanu, Cactaceae of the Mexicau Bouudary, p. 45. 1859. 



