406 Osterhont . — On the Life-History of 
wall and intercellular substance, as well as the cytoplasm, can 
be washed out so as to be entirely unstained, while the 
nucleolus, chromatin, linin, chromatophore, and the refrac- 
tive plates accompanying the pits stain dark blue or black. 
Material stained in toto may be subsequently boiled, and 
employed in making crushed preparations without impairing 
the stain. Such material should remain from one to several 
hours in the haematoxylin. 
External Anatomy. 
The plants are often two to three feet long, varying from 
a light yellowish red to deep red, cylindrical, tapering at the 
base, and attached by a discoid holdfast. The branches are 
numerous, alternately decompound, long and straight, and 
tapering at the base and apex. The antheridia, cystocarps, 
and tetraspores are borne on distinct plants. The three kinds 
of plants resemble each other closely, but the cystocarpic 
plants are as a rule more robust, and are easily distinguished 
by the prominent swellings on the branches, which are 
produced by the immersed cystocarps projecting on one 
side of the branch. The older tetrasporic plants bear on 
their older portions numerous short, simple proliferations, 
which bristle out from the frond in all directions. The 
antheridial plants resemble the tetrasporic, but lack the 
proliferations. 
Histology. 
The cells at the growing-point are small and closely crowded 
together, which makes a study of their arrangement rather 
difficult. By clearing slightly with potash, and by contract- 
ing the cell-contents with glycerine, one can make out in most 
cases a central filament of cells, which gives off on all sides 
lateral branches which grow obliquely upwards, making an 
acute angle with the central filament. Fig. 9 shows the 
