344 M. Tulasne's Researches in Vegetable Embryogeny. 



with embryogeny. At present, far from the hopes of INI. Schacht 

 being realized, or nearly so, I think, that if all discussion with 

 regard to the Horkelian theory must be closed, as he would have it, 

 it is by the condemnation and definitive rejection of this theory, 

 rather than by its undisputed admission into science. Now, 

 more than ever, I feel certain that it is founded upon a mistake ; 

 upon that error in which I formerly shared for a moment, which 

 consists in taking the suspensor of the embryo for the pollen- 

 tube inserted in the embryonal sac. During the past summer 

 I have made a great number of dissections to establish the cor- 

 rectness of the results which I published in ] 849 in the ' Annales 

 des Sciences Naturelles' (3 ser. xii.) j my brother also has de- 

 voted considerable time to similar researches, and we have both 

 always been perfectly convinced, that the embryo, whether ses- 

 sile or stipitate, that is to say, whether provided or not with a 

 suspensor, never, at any moment, had the least real organic 

 continuity with the pollen- tube : the embryo-sac, which is often 

 thickened at its micropylar extremity, receives the close contact 

 of this tube externally (it is even sometimes lodged in a fold of 

 its membrane), but still without ever being torn or perforated 

 by it ; then on its inner face, either opposite to, or at some distance 

 from the extremity of this fecundating filament, it gives attach- 

 ment to the embryo. 



In the Labiat^e, which have especially furnished us with sub- 

 jects for examination this year; in the Pansy, the Almond, the 

 Sloe ; in the Caryophyllaceae, such as the Pinks, the Holosteum 

 umbellatum, L., the Cerastia, &c. ; in the Scroj)hularinese, the 

 Cruciferse, the Fir-tree, and a multitude of other plants, the 

 embryo adheres to the generative sac by a very broad circular 

 base, below which it contracts more or less, and again dilates 

 almost immediately. This base of the embryo, when seen in 

 front, looks like a large aperture in the membrane of the sac ; but 

 this is only an appearance, notwithstanding the opposite opinion 

 of MM. Schacht and Deecke, for it is not very difficult to ascer- 

 tain, as I formerly showed, that the sac is completely closed and 

 continuous where the nascent embryo is implanted upon it*. 

 This fact is of great importance, and contributes not a little to 

 gain the cause for the opponents of M. Schleiden. I add, that 

 the basal disk of the embryo is frequently of much greater dia- 

 meter than the pollen-filament, even when the extremity of the 

 latter, as is often the case, is thickened and enlarged : this cir- 

 cumstance is not more favourable to the Horkelian theory than 

 the absence of a perforation in the membrane of the sac, and 



* See our memoir already quoted in the ' Annales des Sciences Naturelles,' 

 3 ser. t. xii. pi. 3-7, and especially pi. 5. fig. 10. 



