Eo pena ae 
1912) Evans,— Notes on New England Hepaticae,— IX 7 
border visible from above. As seen in cross section the lower surface 
is convex in the median region, the sides rising obliquely and meeting 
the upper surface at a sharp angle. The thickness of the thallus is 
usually about half as great as the width. The epidermal layer is 
composed of thin-walled rounded cells without chloroplasts. These 
soon collapse and either disappear completely or persist as cup-shaped 
vestiges. In most cases the second layer of cells, which are likewise 
rounded and thin-walled, remains intact and assumes the functions 
of an epidermis. 
The plants are monoicous. The capsules are sparingly produced 
and are difficult to discover until the tissue above them has become 
broken down. The spores are brown and average about 100 u in 
diameter in the type specimen and about 90 u in the Connecticut 
material. They agree with the spores of R. Austini in having no wing 
developed at the junction between the convex face and the three 
plane faces. "The whole surface is covered over with a distinct reticu- 
lum which is not interrupted even at the rounded angles of the spore. 
The reticulum is formed by a system of low ridges which project at 
the angles of the meshes as truncate papillae. "These papillae, as 
Howe shows, are 6-9 u long on the convex face of the spore and only 
4-5 u on the triangular faces. He brings out the fact also that the 
meshes on the convex face measure 8-12 u in diameter, while those 
on the other faces are slightly larger. Howe’s account of the species 
is so full that the above description adds no new points of importance. 
The remarkable spores of R. dictyospora will serve to distinguish 
the species from most of the other members of the genus. In size 
and general appearance the plant bears considerable resemblance to 
R. sorocarpa, in which the thallus bears a similar narrow sulcus in the 
apical region. In R. sorocarpa, however, the sulcus is even sharper, 
and the color of the plant is more distinctly glaucous. The species 
is further distinguished by its delicate and hyaline ventral scales and 
by its very different spores, which measure 70-90 u in maximum diam- 
eter and develop a distinct though narrow wing. In R. nigrella DC. 
the thallus agrees with that of R. dictyospora in being bordered bya 
series of slightly projecting purple scales. The spores, however, are 
smaller, measuring 60-80 u, and are further characterized by the 
presence of a narrow wing. R. nigrella is widely distributed in south- 
ern Europe and in North America is definitely known from California. 
According to Austin it occurs also in New York and Pennsylvania, 
