and Genera of Chlorospermous Algae. 407 



My observations lead me to think that the class may be 

 divided into two subclasses. 



Subclass I. MONOPHYTES. 



The zoospores formed within the cells of the plant, isolated ; 

 each zoospore developing into a frond formed of a gradually- 

 developed cell or cells like the parent. 



Order I. Microspore. 



The zoospores small, formed from the endochrome of a single 

 cell. 



Suborder I. Siphonece. 



The plant of a single, tubular, simple or branched cell, not sub- 

 divided into joints, or at length furnished at the tip with a number 

 of simple or branched articulated threads with cylindrical joints. 



I. The cell always undivided. Siphonese verse. 

 A. Zoospores in a distinct sporidium. 



Fam. 1. Codiese. 

 The cells simple, without any internal fibrous network, gene- 

 rally more or less interlaced together, forming a more or less 

 spongy mass. Sporangium lateral, without external antheridia. 



1. Codium. 



Fam. 2. Halimedeae. 



The cell or plant branched, tufted, enclosed in an external 

 coat of carbonate of lime. 



" The Halimedece are generally barren ; the fructifying indi- 

 viduals present little confervoid tufts, divided repeatedly above, 

 and terminating in subglobose fastigiate (inarticulate) branch- 

 lets ; the endochromes of these generally become organized, and 

 produce innumerable active molecules, which doubtless are ca- 

 pable of propagating the plant." (Berkeley, Crypt. 160. f. 42.) 



1. Halimeda. Frond branching, articulate ; the joints flattened. 

 (Harvey, Ner. Bor.-Am. 22. t. 40.) 



2. Udotea. Frond fan- shaped, simple or cleft, on combined stems. 

 (Harvey, Ner. Bor.-Am. 26. t. 40 c.) 



B. Zoospores in the usual cells. Cell free, tufted, branched. 



Fam. 3. Catderpeae. 



The cell or plant free, tufted, more or less expanded as if 

 branched on the sides. 



1. Caulerpa. The cell filled with internal fibres. 



