24 Lin Oe DOGONELMCE AE 
An explanation of such periodicity in this algal group is 
not satisfactorily complete. It seems quite evident that a 
certain time—longer in some species than in others—must 
elapse, during which vegetative development occurs, before 
sexual reproduction takes place. When this vegetative phase 
is completed, it is almost impossible to prevent fruiting, except 
in extremes of temperature, very inadequate light, or toxic 
water. Hodgetts (1921) finds in observations on a small pond 
of Britain that there is some correlation between abundance of 
Oedogonium and (1) higher temperature and (2) competition 
with other alge. We need data indicating the degree of 
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Text Fic. 1. Number of fruiting records each month for the genus Oedogonium, 
showing periods of maximum sexual reproduction. 
relationship between algal growth and reproduction, on the 
one hand, and intensity and quality of light, mineral com- 
position of the water, and hydrogen ion concentration, on the 
other. 
Zoospore production may occur at practically any time 
before the formation of oospores. The germination of the 
zoospores produced directly from the vegetative cells accounts 
in large measure for the number of individual filaments of a 
given species found occupying a particular habitat. 
TAXONOMIC CONSIDERATION. 
In working through a group as large as the Oedogoniacez 
one finds it quite difficult to pass on the validity of some species. 
Such decisions, while always influenced to some extent by 
