Stigonemacece 



321 



of a golden-yellow or brown colour. The branches are generally 

 short, thick, and irregularly disposed. 



Species of this genus occur principally on damp or wet rocks, but are 

 sometimes observed free-floating in ponds and lakes. The largest British 

 species are St. informe Kiitz. and St. mammillosum Ag., the filaments of which 

 reach a thickness of 90 /*. St. hormoides (Kiitz.) Born. & Flah. is the smallest 

 known species ; thickness of filaments 7 15 /*. 



Genus Hapalosiphon Nag., 1849. [? Fischerella (Born. & 

 Flah.) Gomont, 1895.] The filaments are free-floating amongst 

 other Algae, or they are rarely 

 subaerial in moist situations. 

 The primary filaments are never 

 very thick, and consist of a single 

 row (rarely of two rows) of cells 

 enclosed within a strong sheath 

 of uniform thickness. The 

 branches are sometimes of the 

 same thickness as the primary 

 filaments, but more often slight- 

 ly narrower, and they are com- 

 monly unilateral. They are 

 mostly long and flexuose, and 

 are very slightly attenuated. 

 As a rule they are few and 

 distant, but occasionally they 

 arise in unilateral clusters. 

 The sheaths of the branches 

 are always thinner than those 

 of the primary filaments, and 

 generally quite colourless. The 

 cell of the primary filament 

 opposite the base of a branch usually projects into it, and the 

 cells of the branches are proportionately much longer than those 

 of the primary filament. The spores are formed from the ordinary 

 vegetative cells, and possess thick yellowish-brown cell-walls. 

 Often the majority (or even all) the cells of both primary filaments 

 and branches of some portions of the plant become converted into 

 spores 1 . 



Fig. 147. Hapalosiphon Hibernicus 

 West & G. S. West, from Glen Caragh, 

 Kerry, Ireland (x440). E, portion of a 

 row of spores within the sheath. 



1 West & G. S. West in Journ. Bot. June 1897, p. 241. 



w. A. 



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