Present problems in the anatomy, morphology, and biology 
of the Cactaceex. 
W. F. GANONG. 
[Concluded from p. 138. 
The development of the flower is unknown, excepting for 
references by Goebel and others. It is likely to prove of 
great interest, and may throw light upon the relationships of 
the family, as it certainly will of the genera. Biologically it 
is equally unknown, Schumann, Goebel and Loew giving it 
but the barest reference. How is it fertilized? How gener- 
ally are the stamens sensitive or the flowers dichogamous? 
Why sometimes so evanescent? Why are the flowers often so 
Showy? Do they illustrate the principle of showiness in pro- 
Portion to scarcity of insects? Do the colors contrast with 
the background simply, or do they attract particular groups 
of insects? How do the less showy Mamillarias thrive? Is 
self-fertilization common? By what animals is the dissem- 
ination of the fruit effected? How are the dry fruits of 
Echinocactus and some Opuntias scattered? In berries, what 
is the meaning of the white and red colors; do they simply 
contrast with the background, or do they attract specific 
animals? How are bristle-covered Opuntia berries eaten? 
Are they picked at by the bills of birds and neglected by 
mammals? The pulp has been found in several species to be 
formed chiefly by the funiculus of the seed, though the wall 
of the hollowed receptacle co-operates. The extremely ‘‘in- 
ferior” character of the ovary of Cactacee leads us to ques- 
tion whether there be a biological reason for it. If so, is 
it to be found in protection to the ripening ovary, or in 
utilization of the receptacle to help form an edible berry? 
N some species, as Goebel has shown, the seeds germinate 
in the fruit. What does this mean? How are such fruits 
Scattered? Upon the surface of some fruits, new branches 
appear; do they occur when those fruits have seeds: 
Species of Cereus often show a sudden crest, forming where 
the few ribs are replaced by very many. What conditions 
determine this? How does the vegetative point act in the 
transition? The stems of several genera often show a close 
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