389 
Alga-like Organism. 
first simple then di-tri-chotomously branching ; cells oblong, 
12-20 fji long, 6-9 {jl wide ; nucleus centrally located; chro~ 
matophore bright green, usually extending entirely around 
the periphery of the cell ; pyrenoids absent ; pigment-spot 
bright red, situated near posterior third of cell, very variable 
in size ; compartments of filament about the same size as the 
cells, separated from each other by 1-4 cross-walls ; wall of 
filament thin, hyaline ; zoospores same size as vegetative 
cells ; cilia about as long as the zoospores, situated at the end 
nearest the pigment-spot. 
Habitat. — Salt-marshes of the Charles river, Cambridge, 
Mass. The plants grow very close together, forming a green 
velvet on the sides of marsh-grass and other objects on or 
near the surface of the water. Autumn. 
