134 PRINGSHEIM, ON THE IMPREGNATION 



from the contents of the quiescent spore, may be observed to 

 take place in pretty nearly the same way as in Bulbochcete. 



Thus it will be seen that two modes of development of 

 quiescent algan spores, resulting from impregnation, exist. 

 Whilst in one mode, that which obtains in Vauclieria and 

 Achlya, the quiescent spore is developed at once into a young 

 plant ; in the other, Bulhochate, ColeoclicBte, CEdogonium, it is 

 merely the parent of swarming zoospores, which grow into 

 young plants by direct germination. 



That similar sexual conditions occur in the PalmellacecB is 

 almost certain ; at any rate, in them also the existence of red, 

 quiescent spores together with zoospores is indubitable. Thus 

 in GlcBOcapsa ampla the author found, besides the individuals 

 whose cells become zoospores, other cells which acquire thick 

 walls, and become filled with red contents. These forms 

 have been erroneously I'egarded as distinct species. They are 

 in fact the female individuals of the plant. 



Researches are still very much wanted as to the sexual con- 

 ditions of other Algrc, such as the Spirogyrce and Desmidiacece 

 on the one hand, and the Oscillarina, Kutz. on the other, in 

 which nothing like antheridia have been observed, although 

 the author indicates the basilar cells in Rivularia as showing 

 some indications of such being their nature. In conclusion, 

 he thus sums up the result to which he conceives his observa- 

 tions have led : — 



1, That the phenomena presented in Vaucheria and 

 Fucus, establish beyond doubt the material co-operation 

 of the spermatozoids in the act of impregnation, 



2, With respect to the essential nature of the act of 

 impregnation ; it appears that the spermatozoids do not 

 impregnate an already perfectly formed cell, but that the 

 act of impregnation consists in this, that one or several 

 spermatozoids enter the, as yet, membraneless contents 

 of a cell ; that this amorphous substance is not sur- 

 rounded with a membrane until after the entrance of the 

 spermatozoids, which membrane at the same time en- 

 closes the spermatozoids that have effected an entrance. 

 The true embryonic vesicle, therefore, does not exist 

 before impregnation, but is formed subsequently to that 

 act. 



3, With respect to the conditions attending the fructifi- 

 cation of the Algce ; that a sexual propagation takes 

 place in them as well as an asexual multiplication or 

 gemmation. 



The asexual multiplication is effected by means of the 



