238 TouMEY : Fruits of some species of Opuntia 



I' 



The usual form of the fruit of Opuntia versicolor is pear-shaped 

 (fig. 4). It usually contains a number of well-developed, fertile 

 seeds. It is occasionally sterile, and not infrequently shows no 

 vestige of a seed-cavity (fig. 5). Sometimes on the same plant 

 with the forms of fruit mentioned above are found structures which 

 resemble the ultimate branches in almost every respect with the 

 exception that there is a seed-cavity containing fertile seeds In the 

 upper end (figs. 6, 7, 8). Are all of these structures fruit? In 

 this case there seems to be no dividing line between vegetative 

 branch and fruit. The seeds in developing within the branch have 

 influenced only its upper end. Such branches, although they 

 contain seeds, continue indefinitely as a vegetative part of the plant ; 

 often the only external evidence indicating the fruit-character of 

 these structures is the presence of the umbiHcus at the upper end. 



Throughout the genus Opuntia the fruit in its early develop- 

 ment bears numerous leaves in the axils of which vegetative 

 branches as well as flowers may occur (figs, i and 9). 



The fruit of the flat -stemmed species of Opuntia deviates farthest 



F 



in form from that of the normal vegetative branch. In 0. EngeU 

 manni the fruit is usually more or less pear-shaped (fig. 10). In 

 this species as well as in a number of other flat-branched forms, 

 the structure containing the seeds is sometimes large and flattened 

 like the normal vegetative branches (fig. i i). In such cases, how- 

 ever, the whole member does not become pulp-like, change color, 

 and ripen in the fall. Only that part immediately surrounding the 

 seeds '' ripens" as the seeds mature, the remainder continues as a 

 vegetative part of the plant. When the fruit is sterile it often 

 does not ripen at all but remains on the plant for months after the 

 normal fruits have matured. These sterile fruits occasionally 

 produce normal flattened branches (fig. 12) during the second 

 season. 



The following teratological evidence suggests that the present 



Opunti 



formerly 



In the sterile fruit 



of O, Efigelmanni (fig. 13) there is no evidence whatever of a 

 seed-cavity. In this fruit the style persisted for several months 

 after the flower appeared and continued to grow until it reached 

 a diameter several times that of the style in the normal flower. It 



