POLYSIPHONIA 101 



3. Follow the history of the trichogyne through later stages 

 in the development of the cystocarp. Trace the develop- 

 ment of the filaments composing the cystocarp. 

 Eefeeenoe, Principles, Sec. 243. 



Questions. What part of the protoplasm in the female organ 

 corresponds to an egg? Is the structure produced by the 

 fertilized egg a new form of development in your study of 

 the algse ? What is its relation to the sexual plants ? 

 Describe the life history and construct a formula expressing 

 the relationships of the different phases (App. 18). 



98. Batrachospermum. This fresh-water type of the BhodophyceCB is an 

 excellent substitute for Nemalion. Follow a similar outline of study, noting 

 its peculiarities of habit, color, the preliminary growth, Chantransia, if 

 present, etc. 



99. Polysiphonia. From herbarium specimens examine the general growth 

 habits, method of branching, attachment, and color. Note that there are 

 different forms of plants, characterized by different types of reproductive 

 organs. It is simplest to begin the study with the asexual or tetrasporic plant. 



A. The vegetative structure may be studied from any form of the plant. 

 Mount a few filaments. Note under h.p. : 



1. That the filaments are composed of rows of cells, called sipAons, 

 placed end to end and connected with one another by delicate strands 

 of protoplasm ; that the cells contain disk-shaped chromoplasts. Count 

 the siphons, if possible, by focusing up and down. Draw part of 

 a filament. 



2. That the tip of the filament bears clusters of hairs and that it ends 

 in a single cell, the apical cell. 



3. Crush the filaments or cut sections and note that there is a central 

 siphon surrounded by peripheral siphons. Diagram their number 

 and arrangement as they would appear in cross section. 



B. The asexual or tetrasporic plant. Mount filaments bearing tetraspores. 

 Draw : 



1. Part of a branch under m.p., showing position of tetraspores. 



2. A group, or tetrad, of four mature tetraspores surrounded by the 

 peripheral siphons. Note that the spores are contained in a mother 

 cell. 



3. Trace if possible the development of the tetraspore mother cell, deter- 

 mining its origin from the central siphon and final attachment to the 

 latter through a stalk cell. 



