70 PRINGSHEIM, ON THE IMPREGNATION 



and consequently the penetration of the mobile corpuscles, the 

 spermatozoids of the Vaucheria, into the opening, and their 

 continued efforts, as it were, to force themselves into the 

 " cutaneous layer," may be observed with the utmost distinct- 

 ness and precision. In several instances also, after the sper- 

 matozoids had already been for some time within the sporan- 

 gium, I have very distinctly noticed the sudden appearance of 

 a larger, colourless corpuscle at the extreme border of, but yet 

 within, the cutaneous layer (fig. 10), and of which previously 

 not a vestige was perceptible. Its sudden appearance after 

 the impregnation, its superficial position in the " cutaneous 

 layer," its consistence and aspect, allow scarcely any doubt to 

 be entertained that this corpuscle arises from one of the sper- 

 matozoids. I shall subsequently describe a nearly similar 

 thing attending the act of impregnation in the FucacecB, and 

 will here merely advert to the remarkable circumstance that 

 the act of impregnation does not take place between a per- 

 fectly-formed cell and one or more spermatozoids ; but that 

 the action of the spermatozoids is exerted upon the, as yet, 

 unorganized contents of the sporangium, which do not become 

 a cell surrounded with a membrane until after the act of im- 

 pregnation has taken place — the true embryonic cell of the 

 plant. 



With respect to the structure of the spermatozoids of Vau- 

 cheria, I shall here merely remark that when in the mobile 

 condition they present the appearance of elongated slender 

 rods about 1-180'" in size; when killed by means of iodine, 

 whilst in this state, I have never been able to perceive any 

 further structure in them. Whilst those spermatozoids which 

 have ultimately ceased to move after long-continued strug- 

 gling, but without having entered the opening of the sjwran- 

 gium, appear, very distinctly, like minute clear vesicles, also 

 about 1-180'" in size, exhibit a distinct opaque, not brown 

 point, and, as I have seen with the utmost clearness, two cilia 

 of unequal length. Their movement is obviously more like 

 that of the corpuscles of which the contents of the antheridia 

 in Fucus are composed, than that of zoospores. 



1 have stated that the portion of the cutaneous layer left 

 in the sporangium after its bursting, and after the entrance of 

 the spermatozoids, together with the remaining contents of the 

 sporangium, are surrounded with a membrane, and become a 

 cell which completely fills the sporangium — the embryonic 

 cell of the plant. 



The formation of this memhrane of the embryonic cell of 

 Vanclieria is one of the most convincing instances in favour 

 of my views respecting the origin of the cell-wall, in an im- 



