The fruit of Opuntia 



James Arthur Harris 



In the Bulletin of the Torrey Botanical Club for May, 1905, 

 Professor Tourney * presents notes on the fruits of some species 

 of Opuntia, No reference to the literature appears, and this cir- 

 cumstance, in connection with the conclusions drawn from his ob- 

 servations, seems to justify a brief statement of similar observa- 



Op 



e 



Cactaceae^ and some remarks upon his conclusion. No attempt at 

 a complete bibliography is contemplated. 



The writer first considers the dissemination of O.fulgida, and 

 concludes that it is accomplished largely by vegetative means, 

 through the densely spiny and brittle terminal branches ; and that 

 the pendulous clusters of spineless, succulent fruit, which remain 

 for many months on the tree and in easy reach of cattle and other 

 large grazing animals to which it is very attractive, are all impor- 

 tant factors in vegetal dissemination, and that this acquired func- 

 tion of the fruit is gradually influencing its character and its form. 



A 



'* It is certainly changing from its original seed-bearing condition 

 to one of' sterility. * * * Plants of this species are occasionally 

 observed bearing clusters of short, spineless branches which exter- 

 nally closely resemble the clusters of proliferous fruits. These 

 clusters of branches serve the same purpose as the fruits in attract- 

 ing animals. It is possible that they have developed because of 

 the intimate relation between animal life and vegetal dissemination." 

 The writer then refers to a number of species, as 0. tetracantha, 

 0. leptocatdis and 0. arbusada, in which many short, tumid, lat- 

 eral branches not much larger than the fruits are produced in 



abundance during dry and adverse seasons, while under more 

 favorable conditions they are almost entirely replaced by fruit. 



Propagation and distribution in a vegetative manner is un- 

 doubtedly of great importance in Opuntia and has occupied the 



Goebel refers to several species, t 



attention of several writers. 



* Tourney, J. W. Bull. Torrey Club 32 : 235-239.//. 9, 10. 1905 

 t Goebel, K. Pflanzenbiologische Schilderungen x : 70-72. 1889. 



531 



