222 



NEMATOGENJ2. 



< 



( Filaments without a sheath distinct from 

 the trichome ...... 



/3 Filaments agglutinated in small float- 

 ing bundles ..... 



Filaments formed of one or several coloured 

 trichomes enclosed in a transparent sheath, 

 from which the trichomes emerge to repro- 

 i dnce new filaments ..... 



f Sheath containing several trichomes, at least 

 in the larger filaments .... 



A. Filaments growing in scattered 



creeping, erect, or floating wick- 

 like bundles .... 



B. Filaments bundled, erect, growing 



in small rounded tufts, or in felt- 

 like turf of indefinite extent. 

 Trichomes very slender 



Sheath enclosing only a single trichome 



A. Filaments simple, or only excep- 



tionally exhibiting the beginning 

 of ramification where the tri- 

 chome issues from the side of 

 the sheath ..... 



(3 Filaments agglutinated in 

 wick-like bundles . 



B. Filaments branched. Ramifications 



prod need by the branching of the 

 trichome outside the sheath, very 

 irregular, and often geminate, as 

 in Scytonema .... 



Trichomes of which the cells 

 only multiply in the direction 

 of the length of the filament 



Trichomes of which the cells 

 multiply as well in the direc- 

 tion of the breadth of the 

 filament, at least where the 

 branches, which are always 

 produced by lateral multipli- 

 cation, originate 



A. Cells of the trichome often gemi- 

 nate or ternate in consequence 

 of their lateral multiplication, or 

 even forming transverse several 

 celled bands. Sheath large. Cells 

 surrounded with a thick mem- 

 brane very prominent in the old 

 filaments. Hormogones origina- 

 ting in lateral branchlets formed 

 of a single row of cells 



/3 Filaments of the hormogones 

 much slenderer than the 

 principal filament, and origi- 

 nating in unilateral tufts . 



10 SCYTONEME.E 4 



Oscillaria. 

 Trichodesmium. 



c7 



A. B. 



Microcoleus. 



Inactis. 

 A. B. 



Lyngbya. 

 Symploca. 



Plectonema. 



11 



A. B. 



Stiff onema. 



Fiscliera. 



