196 Phillips . — The Development of the Cystocarp 
pericentral cell in N. Hilliae as a ground for the generic 
separation of this species from Nitophyllum , though, from all 
analogy, it would seem to indicate a deep-seated difference. 
Turning now to the diagnosis of the family Delesseriaceae 
as given by Schmitz and Hauptfleisch (’ 97 ) in Engler and 
Prantl’s s Pflanzenfamilien,’ it would seem to require modifica- 
tion in several particulars. 
1. The carpogonial branches are described as 3- or 4-celled. 
In all the species I examined the carpogonial branch was 
invariably 4-celled. I never found the number to vary from 
four cells in the family Rhodomelaceae either. In a recent 
paper on Grinnellia americana , Harv., a monotypic genus of 
Delesseriaceae, which seems to stand near to Delesseria , 
Brannon (’ 97 ), has, it is true, described the carpogonial branch 
as 3-celled, but as he has also stated that it arises directly 
from a central cell, and not from a pericentral cell, it is just 
possible that he has missed the real pit-connexion of these 
cells. Otherwise, Grinnellia differs from all known Deles- 
seriaceae in the origin of the carpogonial branch, as well as 
from those here described in the number of the cells which 
constitute it. 
2 . The carpogonial branches are said to arise singly on an 
inner cell of the cortex. This does not now cover the case of 
N. Hilliae , where they regularly arise in pairs, nor exceptional 
cases of D. ruscifolia , where the same thing occurs. 
3. The external pericarpial wall is described as formed by 
a tearing away of the cortical filaments from the middle layer 
of the thallus. While such a tearing may occur in certain 
species of Nitophyllum with somewhat flattened cystocarps, it 
is certainly not general. In Delesseria , the filaments sur- 
rounding the cystocarpic cavity become strongly curved, 
being pressed back at first by the copious mucilage derived 
from the walls of the sterile derivatives of the pericentral cell, 
and later by the tuft of spore-producing gonimoblast-fila- 
ments. Under this pressure, the cells of the filaments 
elongate, so as to resemble rows of cylindrical cells, yet 
the correlation of part to part in the course of growth is 
