32 BOTANICAL GAZETTE [FEBRUARY 
large multiple bodies with four or more pigmented areas and many 
cilia. Such abnormal spores, of course, have very erratic and 
peculiar movements. Their period of activity is short, few con- 
tinuing to swim actively for more than half an hour. LAGERHEIM 
observed these same abnormal spores, and inferred from them that 
segmentation was successive rather than simultaneous, but, as will 
be seen, this is not the case. 
The zoospores are transparent, except at the anterior end, which 
is occupied by a mass of pigment. After they come to rest the 
nucleus can be seen distinctly as a clear central vacuole. In the 
posterior portions are numerous granules, usually including some 
starch grains. When moving most actively, the zoospores are 
oblong rather than pyriform, as figured by LaceruEmm. Indeed, 
they appear to be narrower in the region of the nucleus than in 
the anterior pigmented end. But this is believed to be due to an 
optical illusion, the more conspicuous region irresistibly appearing 
larger. It is of course not susceptible of careful observation, 
since the shape changes at once when they come to rest. 
If plentifully supplied with fresh water, the zoospores continue 
to swim about actively for several hours. In numerous instances 
they were watched for half a day at a time, and in one case the last 
one on the slide did not perish until 8 hours after liberation. In 
preparations supplied with abundant water conjugation occurs 
but seldom, according to my experience. But when the water has 
evaporated to a considerable extent, all begin to conjugate at once. 
When more water was added, those pairs in which fusion had not 
proceeded too far dissociated rapidly and swam about singly as 
before. From this it was suspected that conjugation might be due 
to the increasing osmotic pressure of the medium consequent upon 
evaporation. On this supposition a few crystals of sugar were 
added to a similar preparation, making the concentration very 
much higher than on evaporation, but this had no apparent effect 
on the zoospores. It was therefore concluded that conjugation 
was induced by an insufficiency in the quantity of fluid present, 
and this conclusion seemed to be confirmed when on placing two 
portions of a culture of zoospores, one in very scanty and the other 
in abundant water, the first quickly conjugated while the second 
