DIVISION INTO GROUPS OR SERIES. 



For purposes of classification the Alga3 may be conveniently grouped under 

 three principal heads or sub-classes, which are, for the most part, readily distin- 

 guishable by the colour of the frond. They are named and defined as follows, viz. 



1. Melanosperme^. Plants of an olive -green or olive-brown colour. Fructifica- 



tion monoecious or dioecious. Spores olive-coloured, either external, or con- 

 tained, singly, or in groups, in proper conceptacles ; each spore enveloped 

 in a pellucid skin (perispore), simple, or finally separating into two, four, or 

 eight sporules. AntJieridia, or transparent cells filled with orange-coloured, 

 vivacious corpuscles, moving by means of vibratile cilia. Marine. 



2. RnoDOSPERMEiE. Plants rosy-red or purple, rarely brown-red, or greenish-red. 



Fructification of two kinds, dioecious:—!. Spores {gemmules, Ag.) contained 

 either in external or immersed conceptacles, or densely aggregated together 

 and dispersed in masses throughout the substance of the frond : 2, Spores, 

 commoxAj csiWadi tetraspores {gemmules, Thw.), red or purple, either external 

 or immersed in the frond, rarely contained in proper conceptacles ; each spore 

 enveloped in a pellucid skin (perisptore), and at maturity separating into four 

 sporules. Antheridia (not observed in all) filled with yellow corpuscles. 

 Marine, with one or two exceptions. 



3. Chlorosperme^. Plants grass-green, rarely a livid purple. Fructification dis- 



persed through all parts of the frond ; every cell being capable of having its 

 contents converted into spores. Spores (Sporidia, Ag.) green or purple, 

 formed within the cells, often (always ?) at maturity vivacious, moving by 

 means of vibratile cilia. Gemmules {Coniocystce, Ag.) or external vesicular 

 cells, containing a dense, dark-coloured, granular mass, and finally separating 

 from the frond. Marine, or, more frequently , living in fresh-water streams, jjonds, 

 and ditches, or in damp situations. 



