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A TEXTBOOK OF BOTANY 



[Ch. X 



Batrachospermum, of clear running waters. The formation 

 of the multispore cystocarp instead of a new plant directly 

 has no doubt the advantage that many new plants are 

 secured from one act of fertilization, as in the analogous 



Fig. 311. — Polysiphonia violacea. 



Left, part of a typical plant ; X 60. Next, portion of a tetrasporic plant, 

 showing tetraspores ; x 150. Next, portion of antheridial plant, showing 

 unripe antheridium, and one emitting the sperm cells ; x 200. Next, above, 

 portion of procarpial plant, showing (shaded) procarp with trichogyne, and 

 the supporting cells ; x 500. Below, a ripe cystocarp ; X 80. 



cases of Ulothrix and Coleochcete; but in Nemalion is involved 

 also another physiological feature (the reduction division) 

 which will later be considered. It is enough to note here that 

 these plants present a regular alternation between sexual and 

 asexual stages or generations, and exhibit another anticipation 

 of the arrangement which becomes very prominent in the 

 higher plants. 



