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1909] ATKINSON—FUNGUS PARASITES OF ALGAE 327 
but is very much elongated. Frequently at the middle it is not much 
larger, while on each side an enlargement occurs (fig. 3, D,’G). The 
_ stimulus which causes the increase in the length and size of the cell 
also increases the development of the chromatophore. When this 
influence ceases the chromatophore begins to degenerate, the color 
Fic. 3.—Rhizophidium s 
showing entrance of germinating zoospores, and mature plant with 
Spo a 
Plants also attached to the host; C mature empty zoosporangia, showing one with the 
Penetration tube on the side; D mature plant, large form, showing hypertrophy and 
Curving of host cell ; £ mature plant with escaping zoospores, showing strongly curved 
host cell; FG showing hypertrophy of host cell; H—M different stages in the opening 
of the 2oosporangium and escape of the zoospores; A-G original; H—M after Zopr. 
fades, the structure breaks down, and the processes of dissolution 
Separate it into small particles with the pyrenoids more distinct, all 
Coalescing into an amorphous mass, which gradually flows toward the 
Middle of the cell where the sporangium is located. This may be due 
Partly to the fact that the cell of the host is larger at that point, as well 
