14 RICCIACEAE 
lumen, thallus-segments commonly with a distinct median sulcus on 
dorsal surface; lamellae of the chlorophyll-bearing layer enclos- 
ing very narrow subvertical air-canals or less commonly larger 
chambers, the latter when present often breaking through to the 
surface, giving the thallus a spongy or lacunose appearance ; ventral 
portions (costa) of the thallus composed of parenchymatous cells 
nearly or wholly destitute of chlorophyll ; a rather poorly defined 
layer of somewhat prosenchymatous starch-bearing cells sometimes | 
distinguishable between the chlorophyll-bearing and ventral strata ; 
cells of the primarily superficial layer of the dorsal epidermis often 
soon collapsed and more or less disintegrated. Stomata repre- 
sented by small pores surrounded by slightly or not at all modified 
epidermal cells. Scales hyaline-albescent, brownish-violet, or dark- 
purple, often fugacious,* rarely surpassing the margins of the 
thallus, originating in a single + median series, soon ruptured along 
the median line and becoming apparently two-ranked. Monoicous | 
or dioicous. Sexual organs scattered, the antheridia irregularly | 
intermingled with the archegonia in the monoicous species. In- 
volucre none. Capsules immersed. Spores large, for the most | | 
part distinctly tetrahedral, the surface marked with free or most 
frequently mesh-forming ridges, the angles of the areolae often with 
papilliform elevations, or the inner (plane) spore-faces sometimes - | 
simply punctate. 
Key to the Species, 
Thallus < ae '” i. e., with very narrow vertical or према air-canals which com- | 
e only inconspicuously with the dorsal surfac 
айа f кып with scales underneath, not ciliate-mar. 
Scales extending considerably beyond the margin, whiisi: -hyaline; spores 1 
mmarginate, obscurely angular, 90-126 и in maximum diameter. 
6. К. Americana. 
* К. crystallina L. is said to have no traces of scales even as rudiments, They 
are scarcely distinguishable in some of the other Californian s 
RR. Americana, nigrella, genere. trichocarpa, Californica, and Сат, 
i 
bons the птици scales are clearly seen in a transverse section to extend uninter- | 
ruptedly a an line and to өй attached to the body ES thallus on either | 
Side; later юч become biseriate by a median longitudinal rup 
Professor Campbell has found in his researches on the жолы of the sexual | 
organs in the Californian Ricciae that ** several of one sort or the other would be formed | 
in succession." We have sometimes had difficulty in finding anything but «ее 
in species that could at other times be clearly shown to be monoicous. 
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