206 Dr. L. Radlkofer oa true Parthenogeneiis in Plants. 



cases of formation of seed n-ithoiit cooperation of the male organs, 

 of the pollen. The more surprising therefore are the proofs of 

 the reality of such cases which are here gathered from the most 

 recent observers. 



In the first rank here must be mentioned the observations on 

 Ccelebogyne ilicifolia, a dicBcious Euphorbiaceous plant, native of 

 Australia, female specimens of which were long since introduced 

 into England, and were widely distributed from there, before 

 the male plant had been detected by travellers in its native 

 country. No living specimens of the male plant have yet reached 

 Europe ; only a dried shoot with male flowers exists in the 

 Herbarium at Kew. A glance at this suffices to show, from the 

 composition of the inflorescence of the plants, the impossibility 

 of the occurrence of a hermaphrodite flower in Ccelebogyne, 

 and to show, further, that if the exceptional case which has been 

 observed in other plants, of a production of male flowers on 

 female specimens of dioecious plants, occurred in Ccelebogyne 

 also, it could not be overlooked. Finally, all botanists who have 

 had an opportunity of examining the female plants of Ccelebogyne, 

 and among these are numerous authorities, agree in declaring 

 that no male organs occur on them. In spite, however, of the 

 fact that the exclusion of the fertilizing pollen of the same spe- 

 cies must here certainly be most perfect, the plants cultivated 

 at Kew annually ripen an abundance of seeds, from which even 

 the third or fourth generation of [female) plants have been raised 

 there. 



Observation of the fact that at Kew the Ccelebogyne is kept in 

 company with other Euphorbiacese, led me to think, while stay- 

 ing there, that the enigma might probably find its solution in 

 the detection of a hybridation. Although this conjecture was 

 very much weakened by the simultaneous observation that the 

 progeny have hitherto preserved entirely the character of the 

 original mother-plant, yet I was more inclined even to the idea 

 that, as an exceptional case, a hybrid might be developed with 

 the characters of only one of its parents, than to believe that a 

 seed, and consequently an embryo, could be developed without 

 previous fecundation. I endeavoured to acquire certainty on 

 this point by the following means : — 



1. An examination of the stigmas of all the ovaries (placed at 

 my disposal by the kindness of Sir \V. Hooker, Director of the 

 Garden), in order to detect if pollen-grains were present ; and 



2. A search through the cavities of the ovaries and the ovules, 

 for the presence of pollen-tubes. 



Among twenty-one ovaries which I examined, I found, upon 

 the stigma of one alone, a dried pollen-grain, which adhered to 

 the surface with other bodies which come under the denomina- 



