No. IO.] FRESH-WATER ALG.E. 71 



Key to Orders. 



Carpogonium developing directly NEMALIONALES 



Carpogonium developing a filament of which two 

 cells conjugate with each other CRYPTONEMIALES 



ORDER I. CRYPTONEMIALES. 



A long branched filament is sent out from the fertilized 

 carpogonium. Each terminal cell of the filament unites with 

 an auxiliary cell, and from the latter the gonimoblasts arise. 



FAMILY I. SQUAMARIACE.E. 



A small group, mostly marine, but with a few fresh-water 

 species. The thallus consists of dense, upright cell-filaments, 

 which form minute, flat, gelatinous or membranous expanses. 

 Cavities in the upper surface of the thallus hold the sexual 

 organs, and, after the fertilization of the carpogonia, are 

 filled with cystocarps. 



Hildenbrandtia Nardo. Thallus crustaceous,- firmly ad- 

 hering, formed of subcubical, blood-red, dark red, rose, or 

 brown cells, placed in close vertical series. Sexual organs in 

 cavities in the upper surface. 



ORDER II. NEMALIONALES. 



The gonimoblasts are developed in tufts, directly from the 

 fertilized carpogonium. 



Key to Families. 

 Thallus with a basal attached portion, from which 

 arise tufts of simple or branched filaments 



LEMANEACE^E 



Thallus filamentous, simple or branched, with sec- 

 ondary axes often in whorls. . .helminthocladiace^e 



FAMILY I. LEMANEACE^E. 



Exclusively fresh-water Alga, growing in very rapid 

 water. The thallus consists of a basal attached portion from 

 which arise dense tufts of erect branched filaments. From 

 these grow the fructiferous branches which are the most con- 

 spicuous part of the plant. After the growth of this part, the 



