Plants, and Parthenogenesis. 87 



reproductiou, evidences of generic difference : I satisfied myself 

 (in 1850) that they are only different varieties of the same act, 

 and may occur in one and the same species, the form being 

 determined by certain relative conditions of nutrition. 



The knowledge of the fructifying process which takes place in 

 the Algae has been pre-eminently promoted by Thuret and Colin, 

 and of that which occurs in the higher Crj'ptogamia by Mette- 

 nius and Hoffmeister. In short, by the careful labours of these 

 and of many other naturalists, it has been incoutrovertibly esta- 

 blished that, besides the multiplication of individual plants by 

 buds or offsets — whether it be a single cell detached from the 

 general mass, or a complex cell-mass, still forming part of the 

 parent plant and developed from it (germ-granules or buds) — 

 there is throughout all classes of the vegetable kingdom, with 

 the exception indeed, at the present day, of the Fungi and 

 Lichens alone, a sexual method of reproduction calculated to 

 maintain the typical form of the species. 



In fact, indications of a process of impregnation were seen, 

 and its reality conjectured, by Ehrenberg in the Lichens and 

 Fungi ; and more recently, Itzigsohn and Rabenhorst, in the 

 case of the Lichens, and Tulasne in that of the Fungi, have 

 detected corpuscles to which they would assign the function of 

 antherozoids. 



I moreover observed a process of fructification in a Lichen, 

 which will serve to establish the opinion that even in these sim- 

 plest organisms a sexual act is performed. Of this observation 

 I shall have to speak hereafter more at large. These various 

 researches respecting the fructifying processes in the Crj^to- 

 gamia make it at the same time evident that the mechanism of 

 the proceeding — i. e. the natm*e and manner of the approxima- 

 tion of two heterogeneous cells, the union of which brings about 

 the production of a new individual of a younger generation — 

 varies so much the more as the structure of the vegetative organs 

 is simpler. Whether the cell containing the fructifying material 

 (pollen, antherozoids, spermatozoids, &c.) be provided or not 

 with a locomotive organ, is of no importance in connexion with 

 the impregnating act. 



The assertions advanced, in opposition to the Linnaean doc- 

 trine, by Spallanzani, Henschel, Schelver, Bemhardi, and others, 

 that the ovules of plants, as a normal condition, are stimulated 

 by the pollen-grains to set up a new development of cells as the 

 foundation of a fresh germ, and that moreover, in like manner, 

 a new germ may be produced without the fructifying influence 

 of the pollen on the ovules, are founded on inaccurate observa- 

 tions, and constitute the framework of hypotheses completely 

 set aside by exact investigations. 



