CONFERVOIDE^E HETEROGAMsE 



223 



first described by A. Braun as the 'rejuvenescence' of a cell, i.e. the 

 transformation of the entire protoplasm of a vegetative cell into a 

 ' primordial cell,' which subsequently invests itself with a new cell-wall, 

 and forms the starting-point of the life of a new individual. In some 

 one cell of a filament, either the terminal or some other, sometimes 

 even in the single cell of which a young filament is composed, the proto- 

 plasm contracts into a globular body which 

 ultimately becomes free by the rupture of the 

 cell-wall, by a transverse slit, into two very un- 

 equal halves. . When this takes place in the 

 terminal cell of a filament or the single cell of 

 a young individual, the upper smaller portion 

 of the cell-wall is lifted up like a lid, or even 

 completely thrown off like a cap. The zoospore 

 thus formed, which in some species is one of 

 the largest and most striking known, has a 

 nucleus, a red 'pigment-spot,' and an anterior 

 hyaline region, to which is attached a tuft of 

 cilia, visible even before its escape from its 

 mother-cell. At the period of escape it is still 

 enveloped in a transparent membrane, which, 

 however, it soon breaks through, and then moves 

 about in the water with great velocity for 

 perhaps half an hour, displaying at this period a 

 number of vacuoles. On coming to rest, the 

 zoospore becomes attached by its anterior hya- 

 line end, loses its cilia, invests itself with a 

 cell-wall, puts out a rhizoid from the point of 

 attachment, and develops into a filament with 

 transverse septa. From the position occupied 

 by the zoospore in the mother-cell, the direc- 

 tion of growth of the new individual must be 

 at right angles to that of the parent-filament. 

 Many of the plants which spring from zoospores 

 are non-sexual, producing nothing but zoospores. 

 (Edogonium is also reproduced by resting-spores (Wille, Bot. Gesell. 

 Stockholm, Sept. 26, 1883; see Bot. Centralbl., xvi., 1883, p. 215). 



The sexual reproduction of (Edogonium still shows a high degree of 

 differentiation of the male and female elements. The antherozoids are 

 very similar in form to the zoospores, but much smaller, and they are 

 provided with a similar tuft of cilia. The antherids are cells belonging 

 to ordinary filaments, but shorter and not containing so much chlorophyll 



cushion of cellulose which 

 has lengthened to the piece 

 of cell- wall, 7t>' in B ; c, cell- 

 caps (magnified). 



