— 68 — 
favorable to their being attacked by lichen-fungi. The only differences 
between the gonidia and the free Algae are such as would naturally follow 
from their different conditions of life. 
2. What the theory considers to be the fungal part of lichens agrees in 
most important particulars with certain non-lichenous fungi, belonging to 
three different orders ; and while the fungal part of some lichens differs 
considerably from the other fungi of their order, there are all gradations 
between these species, and some which cannot be distinguished from non- 
lichenous forms, except by their growing in contact with gonidia. 
3. Gonidia have been separated from lichens and made to grow by 
themselves, when they exhibit all the characteristics of free Algae. 
4. Lichen-fungi have been 
made to grow without gonidia, 
like other fungi, by supplying 
them with organic food in 
solution. 
5. Lichen-fungi have been 
made to grow upon free Algae, 
and upon gonidia taken from 
other species of lichen, and 
produced a regular lichen- 
thallus. 
6. The hyphal part of cer- 
tain lichens is for some time 
entirely without gonidia, and 
gains its nutriment from bark, 
like other fungi; later it feeds 
on Algae. 
Regarding the function of 
gonidia, there is but one 
opinion, namely, that they are 
the food producers of the little’ 
community, and give of their 
abundance to the hyphse, which 
latter in the absence of some 
such supply of organic material could not live. We may compare the lichen- 
fungus to a farmer, and the gonidia to his cattle which yield him food, while 
he in turn shelters them and otherwise provides for their necessities. 
There can be no doubt that the gonidia thrive under the conditions 
imposed upon them, for they multipy so rapidly as to burst through the 
cortex, thus giving rise to the soredia before mentioned. Each soredium is, 
in fact, a tiny cluster of gonidia surrounded by hyphse. When detached and 
carried by the wind to some moist surface favorably situated, it grows into a 
lichen the same as that from which it was derived. Soredia are thus little 
colonies sent out by a parent community. With certain species, especially 
in certain localities, this is the chief — if not the only — method of reproduc- 
tion. It will readily be seen how admirably adapted is this method for 
The same. Vertical section of thallus, 
magnified about 250 diameters. H. . hyphse; 
M., medulla; C. cortex; G., gonidia. (Orig- 
inal ) 
