VI. 
THE SPORE AND ITS DISSEMINATION. 
A work of this character would hardly? be deemed complete 
without some reference to the above subject, which has moreover 
a relation to some of the questions discussed, and particularly of 
spore diffusion in the atmosphere. The largest spore is micro- 
scopic, and the smallest known scarcely visible under a magni- 
fying power of 360 diameters. Taking into account the large 
number of species of fungi, probably scarcely less numerous than 
all the flowering plants, and the immense number of spores which 
some of the individuals produce, they must be exceedingly plen- 
tiful and widely diffused, though from their minuteness not easy 
to be discerned. It has been attempted to estimate the number 
of spores which might be produced by one single plant of Lyco- 
perdon, but the number so far exceeds that which the mind is 
accustomed to contemplate that it seems scarcely possible to 
realize their profusion. Recent microscopic examinations of the 
common atmosphere* show the large quantity of spores that are 
continually suspended. In these investigations it was found that 
spores and similar cells were of constant occurrence, and were 
generally present in considerable numbers. That the majority 
of the cells were living, and ready to undergo development on 
meeting with suitable conditions, was very manifest, as in those 
cases in which preparations were retained under observation for 
any length of time, germination rapidly took place in many of 
the cells. In few instances did any development take place, 
* Cunningham, in ‘‘ Ninth Annual Re port of the Sanitary Commissioner with 
the Government of India.” Calcutta, 187 2. 
