78 



Spuriously branched. Threads or trichomes tufted, not surrounded 

 by slime, but sheathed, provided with interstitial cells. Sheaths 

 firm, in layers. SCYTENEMEACE^:. 



No apparent branching. 



Threads more or less distinctly jointed, sheathed, self moving. 



OSCILLARIACE.E. 



Threads more or less bead-like, not moving, with permanent cells. 



NOSTOCIIACE^:. 



173. Increasing by the formation of free cells within a mother cell. 



PROTOCOCCACE.>:. 



Increasing by cell division. Cells contained in mucus, either single 

 or in clusters. PALMELLACE.E. 



SUB-ORDERS OF DIATOMOPHYCE^). 



174. Provided with radiating spines. Marine or fossil. 



Without sharp-pointed projections, or pointed only at the two 

 extremities. 



Rarely wedge shaped. 175 

 Wedge shaped, but not bent. 



With central nodules in front view, and longitudinal lines in side 

 view. Growing in fresh water. GOMPHOXEME.-K 

 With no central nodules in either view. 



Transverse striae interrupted by an open space. SURIRELLEJE. 

 Transverse striae either very short, or not interrupted by an open 

 space. Mostly marine. MERIDIACE.E. 



175, In front view sometimes nearly rectangular or rhomboidal, some- 

 times equilaterally triangular. Having rounded projections at 

 the corners. Apparently many celled. Valves joined by a band 

 or girdle which is very narrow in the triangular species, but in 

 others is very broad and conspicuous. BIDDULPHIK.K. 



In front view round. Dotted, often radially. In side view appear- 

 ing as flat or convex discs. MELOSIRE^;. 



Not circular and not having rounded projections at the corners. 



