TouMEY : Fruits of some species of Opuntia 239 



became red in color in the late fall, like that of the normal fruit, 

 and developed a central cavity which contained a large number of 

 abortive ovules. In all species of Opuntia the large, thick style 

 has a much swollen base ; it is possible that this is the last rem- 

 nant of what was once the seed-receptacle. 



The adverse environmental conditions under which Opuntia 

 grows is ample reason for this interesting evolution. The ovary, 

 which possibly at one time was superior, has gradually become 

 more and more depressed until now it is entirely enclosed in the 

 fleshy branch. 



Yale Forest School. 



Hxplanation of plates 9 and 10 



Plate 9 



Fig. I. Opuntia fulgida ; cluster of the proliferous fruits: a, fruits with fertile 

 seeds and of the usual pear-shaped form; b^ fruit much elongated, spinescent, and re- 

 sembling a vegetative branch. X f • 



Fig. 2* Opuntia tetracantha ; section of a long, slender branch bearing a short 

 branch and fruit : a^ one of the short specialized branches vi^hich usually become de- 

 tached at the end of the first season. X Vi* 



Fig. 3. Opmtia arlnisctda ; short section from a long, slender branch bearing a 

 short specialized branch (a), and a flower (^). X /£• 



Fig. 4. Opuntia versicolor ; normal pear-shaped fruit. X / 



Fig. 5. Opuntia versicolor ; sterile fruit. X z^- 



Figs. 6, 7, 8. Opuntia versicolor; structures resembling the normal vegetative 

 branches in external appearance, but containing the seed-cavity with perfect seeds at 

 the apex. X 



Plate id 



Fig, 9. Opuntia leptocaulis ; a fruit bearing two long branches, one of which is 

 floriferous. X 



Fig. 10 Opuntia Engelmannt ; normal pear-shaped fruit. 



Fig. II. Opuntia Engehnanni; the seed-cavity with perfect seeds in the apex 

 of a flattened branch. X i* 



Fig. 12. Opimtia Engelmanni ; a sterile fruit persisting until the second year 

 and from which is growing a normal flattened branch, X i- 



Fig. 13. Opuntia Engehnanni ; a sterile fruit on which the style has persisted, 

 " continued in growth, and formed a central cavity in which are many abortive ovules. 



