THE FRUIT OF OPUNTIA FULGIDA. 



A STUDY OF PERENNATION AND PROLIFERATION 

 IN THE FRUITS OF CERTAIN CACTACE/E.^ 



By DUNCAN S. JOHNSON. 



This paper embodies a discussion of the occurrence and significance of a 

 number of striking peculiarities in the development and fate of the per- 

 sistent, self -propagating fruits of certain opuntias. The discussion will be 

 concerned primarily with the perennation and vegetative propagation of the 

 ovary of Opuntia fulgida. This cactus has been chosen for special consid- 

 eration because of its most remarkable power of budding off secondary 

 flowers from the primary ones and also of forming new flowers and vegeta- 

 tive shoots from the long-persistent fruits. 



This investigation has been aided by grants from the Department of 

 Botanical Research of the Carnegie Institution of Washington. Acknowl- 

 edgment is here made to Director D. T. MacDougal for making available 

 to the writer the facilities of the Desert Laboratory at Tucson, Arizona, and 

 of the Coastal Laboratory at Carmel, California. The principal parts of 

 the work have been done at these two laboratories. Other portions of it 

 and much of the writing of this paper have been done at the Harpswell 

 Laboratory, at South Harpswell, Maine, and at Johns Hopkins University. 

 Acknowledgment is also made, for aid in securing material, information, or 

 photographs for this study, to Drs. Forrest Shreve and Hermann Spoehr, of 

 the Department of Botanical Eesearch of the Carnegie Institution, to Dr. 

 David Grifiiths, of the Bureau of Plant Industry, United States Department 

 of Agriculture, to Dr. J. N. Rose, of the Smithsonian Institution, and to Dr. 

 'S. L. Britton, of the ~Sew York Botanical Garden. 



COMPARISON OF THE FRUIT OF OPUNTIA FULGIDA 

 WITH THOSE OF OTHER ANGIOSPERMS. 



One of the almost universal characteristics of the fruit in angiosperms is 

 the comparative brevity of its development. The whole duration of this, 

 from the inception of the flower to the ripening of the fruit and its final 

 separation from the parent plant, or its opening for the discharge of its 

 seeds, is usually less than a year, often very much less. 



The phases of this developmental cycle of the fruit which can usually be 

 distinguished are : First, a period of initiation and maturing of the parts 

 of the flower, which opens for pollination at about the time an egg has been 



^ Botanical contribution from The Johns Hopkins University, No. 56. 



5 



