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Some of these cells, usually shorter than the rest, become 

 tumid, and, without conjugation, have their whole green con- 

 tents transformed into a large spore. Pringsheim has ascer- 

 tained that other cells of the same individual plant have 

 their green contents transformed into a multitude of active 

 corpuscles or zoospores, which, from their subsequent evolu- 

 tion and office, he names androspores ; these escape by the 

 opening of the mother cell moving about freely by the vibra- 

 tion of a crown of cilia attached near the smaller end. One 

 or more of these androspores fix themselves by the smaller 

 end upon the surface of the cell in which a large ordinary 

 spore is forming, or in the vicinity, and germinate there, 

 growing longer and narrower at the point of attachment, 

 while near the free end a cross partition forms, and some- 

 times another, making one or two small cells ; this is the true 

 antheridium : for in it a crowd of spermatozoids are formed, 

 also endowed with motivity by means of vibratile cilia. Now 

 the top of the antheridium falls off as a lid, the spermatozoids 

 escape ; the spore-cells at this time open at the top ; one of 

 the spermatozoids enters the opening, its pointed end fore- 

 most ; this becomes stationary upon or slightly penetrates 

 the surface of the young spore, into which its contents are 

 doubtless transferred, and a coat of cellulose is then, and not 

 until then, deposited upon it, completing its organization as 

 a spore, which in due time germinates, and grows directly into 

 a plant like the parent. 



But in Bulbochsete, and especially in Sphceroplea, so beauti- 

 fully investigated by Cohn ("Annales des Sciences Natu- 

 relles," 4 ser.,v.), the spore does not directly develop into the 

 normal or fruit-bearing plant. Instead of this, by an alterna- 

 tion of generations (to adopt that well understood phrase), the 

 spore proceeds to convert its contents by successive division 

 into a large number of zoospores, different from the andro- 

 spores, namely, small oval or oblong bodies, furnished with 

 two long cilia on a short beak at one end, and for a time mov- 

 ing actively about by their vibration. Coining to rest, these 

 zoospores germinate, by elongation and the formation of trans- 

 verse partitions, into adult tln-ead-like plants, consisting of a 



