69 



Frond having a cellular axis with surrounding bundles of longitu- 

 dinal threads lying somewhat loose in the enveloping mass of 

 mucus. Fruit spores arising from bead-like, jointed threads, at 

 length few, rounded, angular, somewhat large, grouped in no 

 special order. Tetraspores formed in the ends of the horizontal 

 threads, oblong, divided by zones. Growing only in salt water. 

 Species few. DUDRESNAYACE.E. 



155. Fruit spores formed in one or many mother cells. Fruit naked, 

 attached sidewise to the branches. Spores numerous, rounded, 

 angular, grouped in no special order. Frond consisting of a 

 single row of axial cells which are sometimes covered by a layer 

 of cortical cells. Tetraspores variously divided. CERAMIACEJS. 



Fruit spores formed in the terminal joints of articulate threads 

 which are sometimes scattered singly, but are most commonly in 

 groups, pear-form. Frond naked, or having a cortical layer of 

 cells, sometimes partially continuous, but then traversed by a 

 jointed axis. Tetraspores divided triangularly. WRANGELIACEJB. 



Spore groups contained in an external pericarp. 



Spore-bearing threads free, or radiating from a basal placenta. 

 Pericarp with an open mouth. Frond sometimes naked, some- 

 times with a cortical layer of cells. Tetraspores evolved 

 among the cells around the axis of the frond, triangularly divided, 

 definitely arranged. A very large order. RHODOMELACE^:. 



Spore-bearing threads arranged around a central placentar column, 

 radiating upwards, mixed with sterile threads. Tetraspores on 

 the branchlets, near the surface, divided triangularly 



SPYRIDIACE.J;. 



156. Fresh water plants. Growing in fast-running water. Frond thread- 

 like, tubular, olive colored. LEMANEACE.^ 

 Growing in salt water. 



Fruit body consisting of tufted spore threads. Spores formed in 

 each cell of the spore thread, or only in the upper cells, or in 

 the terminal cells. 157 



Fruit body consisting of one or many mother cells, in which the 

 spores are formed by division, and remain surrounded by the 

 transparent membrane or wall of the mother cell, in no special 

 order. 



