118 
THE DUAL LICHEN HYPOTHESIS. 
The only safe method by which these low forms can be deter- 
mined, is by watching their development. In their simple condition 
of cells they are no more than mere buds, the ultimate form of 
which only the rash or foolish would predicate. 
If the gonidia of Lichens are true Algas, it is insufficient to 
state that they so closely resemble Algae that they might be mis- 
taken for such ; there must be some undoubted evidence produced 
that they are Algae in fact, and not in appearance. 
Nylander, on the contrary, holds that they are organs belonging 
to the Lichen. He says, “ I have adduced that the gonidia and 
gonimia of Lichens constitute a normal organic system necessary, 
and of the greatest physiological importance, so that around them 
we behold the growing (or vegetative) life chiefly promoted and 
active.” Again he says, “ The absurdity of such an hypothesis 
is evident from the very consideration that it cannot be the case 
that an organ (gonidia) should at the same time be a parasite on 
the body of which it exercises vital functions.”* 
Now, it must be admitted that Dr. Nylander is the facile princeps 
of Lichenologists If it can be shown that these green cells per- 
form an active part in the life of the lichen — in fact, that they are 
organs possessed of certain functions, then they cannot at the same 
time be foreign to the plant in which they occur. Nylander has 
shown that, whenever they are few in number, a proportionate 
decrease of vitality takes place. That the most vigorous functions 
of life are carried on in their proximity. 
As the Schwendenerian theory is wholly based on the belief that 
there is no genetic relationship between the hyphae and the gonidia 
of the Lichen thallus, any proof that such a genetic relationship 
does exist is fatal to it. Dr. Minks, of Stettin, has directed his 
attention specially to the investigation of this point with very im- 
portant results. He discovers in the hyphas of Lichens two new 
organs, which he has designated geonangium and gonocystium, 
which produce gonidia within the walls of the hyphae themselves. 
These gonidia, because of their minuteness, he names micro-gonidia. 
He has seen these micro-gonidia in all the cells of the hyphae, 
whether in the vegetative or the reproductive parts. He sees them 
in the cortical layer, the medullary layer, the paraphyses, the 
young asci, the sporidia, &c. Thus he has established their ex- 
istence, not only within the hyphee-cells of all parts of the Lichen, 
but also in all stages of its life-history. 
These facts, so utterly subversive of the Scliwendener theory, 
have likewise been observed and confirmed by Dr. Muller, of 
Geneva, who says, “ My results have surpassed my highest expec- 
tations. Not only have I proved the existence of micro-gonidia in 
all the organs mentioned above, after having treated them with 
caustic potash, sulphuric acid, and tincture of iodine, but I have 
also seen them with my excellent immersion objectives, without any 
* Nylander, in “ Grevillea,” ii., p. 146, 147. 
