THE SPORE AND ITS DISSEMINATION. 129 
form of the spores and their size differ materially, as well as the 
manner in which they are produced on the threads. In many 
they are very minute and profuse, but larger and less plentiful 
in the Dematiei than in the Mfucedines. The spores of some 
species of Helminthosporium are large and multiseptate, calling 
to mind the spores of the Melanconici. Others are very curious, 
being stellate in Triposporium, circiuate in Helicoma and Helico- 
coryne, angular in Gonatosporium, and ciliate in Menispora cili- 
ata. Some are produced singly and some in chains, and in some 
the threads are nearly obsolete. In Peronospora, it has been 
demonstrated that certain species produce minute zoospores 
from the so-called spores. The dissemination of the minute 
spores of the Alucedines through the air is undoubted; rain also 
certainly assists not only in the dispersion of the spores in 
this as in other groups, but also in the production of zoospores 
which require moisture for that purpose. The form of the 
threads, and the mode of attachment 
of the spores, is far more variable 
amongst the Afucedines than the form 
of the spores, but the latter are in all 
instances so slightly attached to their 
supports as to be disseverel by the 
least motion. This aids also in the 
diffusion of the spores through the 
atmosphere. 
Sporanuia are produced in the 
Physomycetes usually on the tips or 
branches of delicate threads, and these when mature dehisce and 
set free the minute sporidia. These are so small and uniform 
in their character that they require but a passing mention. 
The method of diffusion agrees much with that of the ALucedines, 
the walls of the sporangia being usually so thin and delicate 
as to be easily ruptured. Other modes of fructification prevail in 
some species by the production of cysts, which are the result of 
conjugation of the threads. These bodies are for the most part 
furnished with thicker and more resistant walls, and the diffusion 
of their contents will be regulated by other circumstances than 
: ME 
Fic. 63.--Spores of Helicocoryne. 
