226 NEMATOGENZ, 
a Spores measuring ‘004 x -008 mm. or more. 
1. Sheaths confluent, trichomes scat- 
tered, irregularly interlaced. 
* Spores rounded oval - . 10. collinum. 
** Spores oval. ae ge a . 11. MUscoRUM. 
2. Sheaths wel] defined, and separable 
by pressure, trichomes folded ver- 
tically and parallel : - «12. Passerinianum. 
8B. Spores measuring 004 x ‘006 mm. or more. 
* Mucilage tolerably firm ; tri- 
chomes olive. Spores oval . 13. HUMIFUSUM. 
** Mucilage soft, easily diffluent, 
trichomes eruginous green. 
Spores subglobose . .  . 14. ealcicola. 
B. Fronds deformed, hollow ; joints spherical 
compressed . i Ate Na » «+  . 15. foliaceum. 
IV. Comuunta. 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 . s . 16. COMMUNE. 
V. SpH#RIcA. Fronds globose or subglobose (often becoming irregular 
when they grow large), limited by a firm and resisting peridermic 
coating. 
A. Terrestrial species, or sometimes inundated. 
a Trichomes not fusiformly swollen be- 
tween the heterocysts. 
1. Fronds attaining 1 m. and more. 
Trichomes torulose. 
* Frond firm, trichomes com- 
pact, joints cask-shaped, or 
compressed. spheerical close to- 
gether, uniform; spores oval, 
smooth .. es . 17, SPH#RICUM. 
** 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. 
6 Trichomes fusiformly swollen between 
the heterocysts ; joints dissimilar, the 
one kind straight and elongated, the 
other larger and spherical; spores 
spherical, rough . F : ‘ . 20. spheroides. 
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. CHRULEUM. 
