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IN VEGETABLE BIOLOGY. 369 
peeuliar modifieation of cellulose of which the wall is originally 
composed has been converted into either gum or mucilage ; but 
this does not appear to be the case, for I could find no trace of 
swelling with caustic potash, and corallin soda was not taken up 
to the slightest extent *. From the fact of iodine and sulphuric 
acid imparting no blue or violet tinge the presence of gum rather 
than mucilage might be inferred, and possibly there may be some 
forms of gum whieh refuse to take up corallin soda. But this 
being doubtful, Lam forced to content myself with calling the 
swollen-up substance “gelatinous matter" for want of a more 
precise term. 
Coenobial Zoospores. 
The original idea with which this research was entered upon, 
viz. that the exserted cilia imply a coenobial phase, was found to be 
eorrect under certain circumstances; and we will now consider 
these additional methods whereby the Apiocystis zoospore is 
enabled to escape into the surrounding medium. A good instance 
of this will be seen on Pl. LVI. fig. 25; herethe gonidia lie, for 
the most part, in pairs within a common investing wall. On 
carefully examining the surface of the zoosporangium, openings in 
it approximately equal in extent to that of the investing wall were 
seen (a in the above figure): an opening denoted by the letter b 
is seen from the side; through this a small ecnobium (c) has 
made its escape. When first seen, the coenobium, which re- 
sembled in every way the pairs of gonidia still upon the zoospor- 
angial wall, was quite close to the opening; but by the time 
that it was drawn (about a day after its first discovery) it had 
become separated from the wall. It was not motile, however, 
being retained in position and its cilia being prevented from 
moving by surrounding gelatinous matter. Fig. 15, Pl. LV., shows 
a somewhat similar condition of things, which was of frequent 
occurrenee, but only during warm weather. All efforts to libe- 
rate such coenobia by inducing currents of water upon the glass 
slide proved unavailing ; and the zoosporangium from which 
fig. 25 was drawn was kept under observation for several days 
without any ensuing change. I shall refer to this matter 
later on. 
That Apiocystis really produces small coenobia similar to those 
* On these points vide Bower, ‘Practical Botany, ed. 2, part i. p. 41, and 
App. B. 
