440 Dr. W. Hofmeister on the- Fecundation of the Coniferse. 



servations to speak directly in favour of his assertion that the 

 said cell-rosette is formed from the pollen-tube by " tying-ofF" 

 {abschniirung) . 



My later researches, made principally upon Pinus canadensis, 

 have led me to the conclusion that the appearance of the first 

 cell of the pro-embryo in the bottom of the corpusculum is a 

 secondary condition. Many times, in corpuscula into or upon 

 which pollen -tubes had penetrated, I detected in the middle of 

 the corpusculum fvee, ovate cells, distinguished above their neigh- 

 bours — unimpregnated germinal vesicles — by size, and above 

 all by the extremely abundant granular mucilage they contained, 

 in the same way as is the case in the impregnated germinal 

 vesicles of Biotia and Juniperus. That these cells gradually 

 make their way to the bottom of the corpuscula is rendered still 

 more probable, since the undoubtedly unicellular forms of the 

 pro-embryo of Pinus canadensis are made to draw back far away 

 from the lower concavity of the corpusculum, by the application 

 of reagents contracting the primordial utricle; a certain proof 

 that they at first lie loose here. Hitherto I have not observed 

 these cells — in my opinion the impregnated germinal vesicles — 

 in immediate contact with the pollen-tube. In the cases where 

 they were nearest to it, they were always at a distance at least 

 equalling the longitudinal diameter of the cell. But it is never-^ 

 theless probable, that there is always direct contact in the im-^^ 

 pregnation. This would explain the coincident observations of 

 Scheljesnow * and Cienkowski t, according to which, in Larix 

 europcea (which I have not yet examined), a large cell hangs fojTjjj 

 a long time to the pollen-tube which has penetrated the corpus- 

 culum. The fecundation seems to be efiected more slowly here 

 than in the other Abietinese. 



I have little to add to my former statements regarding the 

 cell-formation in the interior of the pollen-tube of the Abietinese. 

 During the impregnation I saw in its interior, with free starch, 

 spherical cells with granular mucilaginous contents, sometimes 

 combined in groups, and then eight in number. Not the least 

 sign can be observed of an opening of the pollen-tube. The 

 two modifications of its mode of penetration already mentioned 

 as occurring in the Cupressinea? and Taxinese, are met with also 

 in the Abietinese. While it frequently advances only as far as 

 the upper concavity of the corpusculum, it still more frequently 

 projects a hemispherical end a little way in, and sometimes pene- 

 trates tolerably deeply. I possess a preparation of Pinv^ cema^' 

 densis in which it fills up a full third of the corpusculum, mmlf^^d 



^ ; * Bulletin de Moscou, 1849, p. 46g} gu a^ge ^i aC^og gift 



