Dr. L. Radlkofer on true Purtheaoyenesis in Plants. 207 



tion of dust. No pollen-tube could be observed in this case. 

 It is further to be remarked, that no embryo could be found in 

 the ovules of this ovary, although it was at the proper age. 



Each ovary contains three ovules. In none of these could be 

 discovered a pollen-tube, by the most careful examination, in 

 which, by longitudinal sections and subsequent dissection with 

 the needle, the path which the pollen-tube must have taken, 

 down to the embryo-sac, was visibly exposed. Neither could 

 any be found in the cavity of the ovary, outside the ovules. 



In other Euphorbiacese, chosen for comparative investigation, 

 whose ovaries and ovules had essentially the same structure as 

 those of Ccelebogyne, and presented neither more nor less diffi- 

 culties than Ccelebogyne for the discovery of the pollen-tubes in 

 their course from the stigma to the embryo-sac, a pollen-tube 

 was readily demonstrated in the interior of the ovules. 



Notwithstanding this absence of pollen-tubes in Ccelebogyne — 

 in two-thirds of those ovules which were neither too young, nor 

 were rendered abortive by the overpowering growth of their 

 neighbours, — of the three ova (germ- vesicles) which were con- 

 tained in each embryo-sac, sometimes all, sometimes two, and 

 sometimes only one, were developed into young embryos, and the 

 particular stages of development in the formation of the em- 

 bryo were found to be perfectly in agreement with those which are 

 passed through, in other Euphorbiacese, after fecundation has 

 taken place. 



After these observations, the idea of a hybridation in Ccelebo- 

 gyne must be given up. I think that I am rather warranted in 

 concluding from them — with the same certainty as Von Siebold 

 derived from the numerical proportion of the positive and nega- 

 tive results of his observations on the presence of spermatozoids 

 in tl^e eggs of worker- and drone- bees — that in Ccelebogyne the 

 embryo really can be developed without a previous fecundation of 

 the ovum, 



A testimony in favour of the correctness of this assumption 

 is furnished by the behaviour of the stigmas of our Coelebogyne- 

 plants, upon which the first observer of the Parthenogenesis of 

 Catlebogyne, J. Smith*, very properly laid great weight. 



In all plants which are regularly fertilized, in which a suffi- 

 cient number of pollen-grains arrive at the stigmas of the ovary, 

 to provide the ovules with the requisite pollen-tubes, the expan- 

 sion of the ovary, which takes place simultaneously with the 

 development of the embryo, is the signal for the decomposition 

 of the stigmas : they wither, dry, and mostly separate from the 

 ovary. The delivery by the cells of the stigma of the material 



* Linneean Transactions, xviii. p. 509. 



