Dr. L. liadlkofer on true Parthenogenesis in Plants. 205 



researches now before us, either in its totality or in part, as the 

 proper fecundating power, as the actual fecundating substance, — 

 correspond the spontanea uslij moving form-elements {spermatozoids) 

 in the fcrtihzing (spermatic) fluid of plants. In some Algfc and 

 in the Phanerogamia only are these form-elements wanting in 

 the fecundating Huid ; the fertilizing fluid itself appears in these 

 cases as the fecundating substance. 



Throughout the vegetable, as in the animal kingdom, the act 

 of fecundation is completed by the fecundating matter — whether 

 it possesses an independent form or not — coming into immediate 

 contact with the vegetable ovum and its contents*. This is the 

 case in particular in the Phanerogamia, as I have placed beyond 

 all doubt by my investigations f. As we shall have in the sequel 

 to speak more minutely, and exclusively, of this, it is requisite 

 to sketch briefly the process of fecundation in the Phanerogamia, 

 and in so doing, we may take the liberty, for the sake of sim- 

 plicity, to omit all reference to the fecundating processes of the 

 Coniferse and Cycadese, which deviate from those of the rest of 

 the Phanerogamia in many respects. 



The ovum to be fertilized, the germ-vesicle, is contained, in 

 the Phanerogamia, in a large cell, the so-called embryo-sac, 

 which itself constitutes the centre of a variously constructed, 

 cellular organ, the seed-bud {gemmula — hitherto inconveniently 

 termed ovulunt). This seed-bud (ovule) it is which, when per- 

 fectly developed, becomes, in its mature condition, the seed. It 

 is enclosed in the germen or ovarium, and usually a number of 

 these ovules occur in the same ovary. 



The fecundating matter consists of the contents of isolated 

 cells, the pollen- grains. If one of these pollen-grains arrive at 

 the proper part of the ovary, upon the stigma, it undergoes 

 further development. The cell of which it consists grows, be- 

 comes tubular [pollen-tube), and penetrates through all the 

 parts lying between the stigma and the embryo-sac, so as at 

 length to allow its contents to pass over into the embryo-sac 

 and germ- vesicle, by endosmose, and thus to render the germ- 

 vesicle capable of further development, of forming an embryo. 



It is no wonder, in the face of the observations on the material 

 participation of the fecundating substance in the formation of a 

 new plant {i. e., in the Phanerogamia, the formation of seeds), 

 mentioned at the beginning of this paper, that little faith 

 came to be placed in the accounts of the earlier botanists, of 



* For tiie further explanation of the conditions here referred to, I would 

 direct the reader to my recent treatise " Befruchtungsprocess im Pflanzen- 

 reiche," &c., Leipsic, 1857- [A translation of this will short!}' appear in 

 our ])ages. — Ed. Ann. Nat. H'.9^] 



t Radlkofer. Die Befrnchtitng dev Phanerogamen. Leipsic, 1856. 



