590 . DESMIDS AND DIATOMS. 
which the “connecting membrane” has merely become 
slightly enlarged, to those in which it may be seen to 
contain two new individuals; these latter ready, by the 
disruption of the membrane, to acquire a separate exist- 
ence, or, as is more commonly the case, to still maintain 
some slight connection with the parent cell, thus forming 
new members in a compound community. 
The rapidity of this budding process is something 
astounding, and goes far to explain the geological impor- 
tance of these organisms. Ehrenberg, the great micros- 
copic observer, in alluding to this subject, observes that 
“the silicious infusoria (Diatoms) form, in stagnant waters 
during hot weather, a porous layer of the thickness of the 
hand. Although more than 100,000,000 weigh hardly a 
- grain, one may, in the course of half an hour, collect a 
pound’s weight of them ; hence it will no longer seem im- 
possible that they may build up rocks ;” and Professor 
Smith, the author of a standard work on these organisms, 
has calculated, as the progeny of a single diatomaceous 
cell, the amazing number of one thousand millions in a 
single month. These facts are certainly calculated to 
awaken our astonishment, yet wonderful as they are as 
illustrations of the reproductive power, they are but a 
repetition of what actually occurs throughout the whole 
vegetable kingdom. Take for example the century plant 
of our conservatories. An excellent authority tells us 
_ that, shooting forth its flower-stalk at the rate of a foot 
in twenty-four hours, it actually produces no less than 
twenty thousand millions of cells in a single day; and 
many other plants, in a greater or less degree, illustrate 
the same fact. In both cases the new cells are micro- 
scopic, but while in the higher forms they remain aggre- 
_ gated to produce a close and compact structure, of a more 
