Harris : The fruit of Opuxtia 533 



3. It has become caulome by its once superior ovary receding 

 into a vegetative branch, thus making it at present inferior. 



4. The branch which now becomes the ov^ary is usually modi- 

 fied and ripens into the structure which we term the fruit; it may 

 however become but Uttle modified, resembling the ultimate 

 branches and continuing as a vegetative part of the plant. 



The first of these conclusions may be freely admitted in so far 

 as any fruit developing from an inferior ovary is to be regarded as 

 caulome. In the Cactaceae the similarity of the portion of the 

 fruit derived from the receptacle to the vegetative shoot is greater 

 than in many other forms with an inferior ovary, and the terato- 



fTc 



b 



resemblance than those furnished by the normal structures. It 

 seems however unnecessary to discuss all the teratological evi- 

 dence,* since the case is one largely parallel with that of replace- 

 ment of floral organs by foliage leaves. If one accepts the latter 

 as proof that the elements of the flowers are derived from foliage 

 leaves, he will also regard the fruit of Opuntia-d.^ derived from the 



vegetative branch. 



The proposition that the fruit of Opuntia is caulome in struc- 

 ture is by no means new. It would require an unprofitable 

 amount of labor to try to locate the first suggestion to this effect, 

 but it was certainly more than fifty years ago. 



The second statement, that the caulome nature of the fruit is 



■ 



probably of recent development, seems to be open to question. 

 It may be quite true, but no valid evidence is offered in support 



of it. 



ibryol 



no evidence in favor of this point, and our knowledge of the rela- 

 tionships of the Cactaceae is too obscure to permit of valid deduc- 

 tions without an examination oi all accessory data. It is, however, 

 a quite general opinion that the Cactaceae as a group is of recent 

 origin, but the relationships of the groups are very uncertain. 



The third assertion, that the fruit has become caulome by its 

 once superior ovary receding into a vegetative branch, thus making 

 it at present inferior, is also much in need of supporting evidence. 

 Here again the evaluation of teratological evidence for special 

 morphological conclusions must largely decide the problem. 



*For much oi" which the reader will consult Tenzig's Pflauzenteratologie. 



