(Edogoniacece 63 



position ; and at other times there is a distinct apical lid to the 

 oogonium. An antherozoid finds its way through the opening into 

 the oogonium, frequently having to accommodate itself to a passage 

 much narrower than itself, and unites with the oosphere at the 

 region of the receptive spot. After the fusion of the nuclei of the 

 antherozoid and the oosphere the latter becomes the fertilized 

 ovum or oospore, and it immediately surrounds itself with a cell- 

 wall. The oospore then rests for a longer or shorter period, its 

 chlorophyll disappears, its cell-wall increases in thickness, and its 

 protoplasm becomes tinted with a red or brown pigment and filled 

 with oil. On the decay of the walls of the oogonium the oospore 

 is liberated and on germination its outer wall bursts and the 

 contents, surrounded by a delicate membrane, are set free. With 

 few exceptions a new plant is not immediately formed from the 

 oospore, but the free cell-contents usually divide into four cells, 

 each of which forms a rounded ciliated zoospore. The zoospores 

 represent a rudimentary sporophyte generation, and after swarming 

 for a while they come to rest and form new filaments. Sometimes 

 the filaments formed from the zoospores are asexual and they give 

 rise to several other asexual generations before forming a sexual 

 plant. If the zoospores become fixed at once to some substratum, 

 they form a hemispherical or spheroidal cell from a circular opening 

 in which the new filament arises 1 . If they do not become fixed 

 before germination haptera are usually developed (fig. 10 A I). 



The principal investigators of this family of AlgaB have been 

 Pringsheim and Wittrock, and quite recently it has been splendidly 

 monographed by Him 2 . 



Genus CEdogonium Link, 1820. The plants of this genus are 

 simple filaments with cylindrical cells usually slightly swollen at 

 their upper extremities. The apical cell is generally terminated 

 by an acutely conical cap or more rarely by an elongated bristle. 

 The strong cell-walls and the swollen upper extremities of the 

 cells, some of which possess the peculiar transverse striation, are 

 characters which readily distinguish even sterile species of this 

 genus from all other filamentous green Alga3. The adult plants 

 usually occur floating in masses or they may remain attached to 

 various water plants, and as the mucous covering on the exterior 

 of the filaments is very slightly developed, they not only serve. as 



1 Scherffel in Ber. Deutsch. Bot. Ges. xiK, 1901. 



2 Hirn in Acta Soe. Scient. Fennicse, xxvii, 1900. 



