RicciA 29 
tical-obovate, obtuse or subacute, narrowly canaliculate, the mar- 
gins often brownish, acute, entire, slightly membranous, becoming 
rather obtuse toward the base, often erect-connivent on drying ; 
width of transverse sections 1-2.5 (mostly 1. 5-2) times their 
height, their ventral boundary nearly rectilinear, slightly convex 
toward the apex, the air-chambers narrow and inconspicuous ; 
epidermis of a single layer of cells, these lightly protuberant, sub- 
quadrate in vertical section and often broader than high, 2 5-40/! 
X 25-45 и, filled with а transparent and colorless ог slightly gru- 
mous, somewhat refringent fluid, collapsed and disintegrated only 
in the oldest parts of the thallus: monoicous : antheridial ostioles 
but slightly or not at all elevated: capsules often numerous, 
crowded together near the bases of the segments, hemispherical- 
protuberant above together with the naked, usually light brown, 
long intact covering, this commonly with a small purple spot about 
the exserted archegonium-neck ; spores brown, becoming darker 
and more opaque with age but usually translucent in glycerine, 
60-78 и in maximum diameter, angular, with a minutely granular 
or nearly smooth, sometimes interrupted margin 3-6 и in width, the 
outer face with irregularly anastomose-reticulate ridges, lightly 
papillose or almost smooth in profile, the inner faces usually finely 
and Somewhat regularly reticulate, with thick-walled meshes. 
Exsicc. Hep. Bor.-Am. 1405. 
Hep. Am. 165. 
In rather dry exposed places, especially about rocks, often ac- 
companied by Аса trichocarpa and К. minima. 
San Francisco: near the Ocean House (Bolander) ; hills above 
the Mission Dolores (Howe); Wildcat Сайоп, near Berkeley 
(Howe), Fruit Vale (Miss Byxbee); Mitchell's Cañon, Mt. Diablo 
(Howe); Pasadena (McClatchie); Twin Oaks, San Diego Co. 
(Е. W. Koch). 
The Pasadena plant (А. aggregata Underw.) differs from the 
European and from the specimens of the San Francisco region in 
the more regularly and finely reticulate outer face of the spore, 
but this character shows considerable variability even in the Pasa- 
dena specimen and hardly justifies, we think, a specific separation. 
The dorsal epidermis іп A. zgre//a is very different from that 
of any other Riccia we have examined. Its cells are for a long 
time turgid with a nearly transparent fluid which takes an intense 
violet stain when sections of the thallus are treated for several 
hours with solutions of haematoxylin. We found especially fa- 
