I20 Americati Quarterly Microscopical Journal. 



contents the spermatozoids, which escape in great numbers into ' 

 the surrounding water on the rupturing of the cell-wall. 



The others of these reproductive branches differ materially 

 in form and history from those just described. They have 

 greatly more chlorophyll, and the cell-contents are much more 

 closely compacted. The cells swell out into egg-shaped bodies, 

 and are closely filled with globules of chlorophyll and oil. 

 These are the oogonia. The outer cell-wall of the oogonium 

 is finally ruptured, when the spermatozoids which have been 

 previously, or at the same time, liberated from a neighboring 

 antheridium, press in and mingle with the cell-contents of the 

 oogonium, and fructification takes place. Then the fructified 

 oosphere clothes itself in a thick cell-wall and enters upon its 

 resting period. " In the Vauchcria the formation of the or)gon- 

 ium and antheridium begins at evening ; by the middle of the 

 next forenoon they will be perfect, and between lo and 4 

 o'clock of that day the fructification will takeplace." Sachs, 

 Lehrb., p. 214. 



The genus CEdogo?iiuni presents some peculiarities of fruc- 

 tification worthy of notice, and although Pringsheim, some 

 years ago, studied and wrote the life-history of this plant, 

 there are still some points which need further elucidation. 



The oogonium and antheridium of this genus are pro- 

 duced by changes in the vegetative cells of the same plant — 

 the former by the swelling and rounding of the cell and the 

 thickening and final segregation of the cell-contents ; the lat- 

 ter by the transformation of the cell-contents into motile sper- 

 matozoids. Plate XI., Fig. 2, A, represents a fragment of the 

 middle part of a fertile thread of (Edogonium ciliatum magni- 

 fied 250 times. At«, the plant cell has developed into an oogon- 

 ium, and at /', several cells have undergone the necessary 

 change to make of them antheridia, whence spermatozoids will 

 emerge and fructify the oospore at a. 



At the same time with the oogonium, there is formed in other 

 plants of the same species, a peculiar kind of swarm-cell which 

 fastens itself to the side of the oogonium, and grows into a 

 singularly-shaped male plant, or antheridium, called by the 

 Germans, a "Dwarf-man," from the cells of which come sper- 

 matozoids, which fructify the oogonium upon which it is para- 

 sitical. Fig. 2, B, represents an oogonium {6) of O. ciliatum, 

 at the moment when it is being fructified by the entrance into 



