Grinnellia americana , Harv. 
23 
held firmly together and placed in dilute gum-arabic on the 
freezing chamber. In a few minutes it is frozen sufficiently 
for sectioning. 
The sections in this work were cut *03 mm. in thickness, 
and, mounted in dilute glycerine, were ready for examina- 
tion. 
In some cases sections were stained with Delafield’s haema- 
toxylin in order to bring out distinctly the thin gelatinous 
coat which surrounds the procarpic cells and, in more advanced 
stages of the cystocarp, the thick cell-walls of the auxiliary 
cells and ooblastema-filaments. 
To summarize the chief points developed in the study of 
Grinnellia americana : — 
1. Grinnellia americana is distinctively an American marine 
Alga. It was erected into an independent genus by Dr. Harvey. 
2. There are no distinctive differences in the vegetative 
structure of the male, female, and tetrasporic fronds. 
3. This Alga flourishes most luxuriantly in quiet waters. 
In such conditions the fronds separate from their holdfasts 
late in the summer ; and, rising to the surface, are carried 
away by the shore-currents, thus effecting a wide and whole- 
sale distribution of the fruiting bodies. 
4. The cells, vegetative and reproductive, are nucleated, 
surrounded by thick cell-walls and, with one exception, con- 
nected with one another by protoplasmic pits. In the case 
of the exception, the cells of the procarp, they are connected 
by open pores. 
5. Adult plants are very sensitive to intense light and 
increasing temperature ; but, on the other hand, will not grow 
in shady places. 
6. Mutilated plants proliferate readily, and thus a single 
frayed frond may give rise to a large number of vegetatively- 
produced plants. Not only do these proliferations develop 
when injured, but the female plants frequently bear prolife- 
rations, in the terminal end of which may be found a cysto- 
carp, which appears pedicellate. 
Plants may originate vegetatively by regeneration of the 
