226 NEMATOGEN.E. 



a Spores measuring '004 x '008 mm. or more. 



1. Sheaths confluent, trichomes scat- 

 tered, irregularly interlaced. 



* Spores rounded oval . . 10. collinum. 

 ** Spores oval . . . .11. MUSCOBUM. 



2. Sheaths well defined, and separable 

 by pressure, trichomes folded ver- 

 tically and parallel . . .12. Passerinianum. 



&. Spores measuring *004 x -006 mm. or more. 



* Mucilage tolerably firm ; tri- 

 chomes olive. Spores oval . 13. HUMIFTJSUM. 



** Mucilage soft, easily diffluent, 

 trichomes seruginous green. 

 Spores subglobose . . .14. calcicola. 

 B. Fronds deformed, hollow ; joints spherical 

 compressed 15. foliaceum. 



IV. COMMUNIA. Terrestrial species (sometimes inundated). Fronds at 

 first globose, then becoming tongue-shaped, plane, or irregular, not 

 adherent. 



Adult frond suborbicular, folded, undulate, 

 entire or lobed, often perforated ; joints 

 spherical-compressed, uniform . . .16. COMMUNE. 



V. SPHJERICA. Fronds globose or subglobose (often becoming irregular 

 when they grow large), limited by a firm and resisting periderrnic 

 coating. 



A. Terrestrial species, or sometimes inundated. 



a Trichomes not fusiforrnly swollen be- 

 tween the heterocysts. 



1. Fronds attaining 1 m. and more. 

 Trichomes torulose. 



* Frond firm, trichomes com- 

 pact, joints cask-shaped, or 

 compressed sphasrical close to- 

 gether, uniform ; spores oval, 



smooth 17. SPHJERICUM. 



** Fronds soft, trichomes much 

 spaced out, of unequal size, 

 joints nearly spherical, sheaths 

 often coloured, contrasting 

 with the generally uncoloured 

 mucilage ; spores oval, smooth 18. RUPESTRE. 

 2 Fronds very small, punctiform, not 

 attaining 1 mm. 



Trichomes large ; joints cylin- 

 drical, a little constricted at the 

 point of junction ; spores glo- 

 bose, smooth . . . .19. MACROSPORUM. 

 /3 Trichomes fusiforrnly swollen between 

 the heterocysts ; joints dissimilar, the 

 one kind straight and elongated, the 

 other larger and spherical ; spores 

 sphaerical, rough 20. spTiceroides . 



B. Aquatic species (colour blue, or approach- 

 ing to blue). 



a Trichomes dissimilar, unequal ; joints 

 of two forms, the one (young) elon- 

 gated, the other large, spherical, often 

 filled with opaque granules . . .21. CCERULEUM. 



