Grinnellia americana, Harv. 23 



held firmly together and placed in dikite 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 



