The Status of the Algo-Lichen Hypothesis, 5 
er, and Th. Fries, oppose the theory of "dualism of lichens." 
There are, however, several different ideas as to the origin of the 
gonidia. Fries holding one opinion, Nylander another, and Crombie, 
taking a mean between the two, seems to believe either. Muller 
supports the " micro-gonidia " theory of Dr. Minks, as did the la- 
mented Professor Tuckerman. Nylander, while acknowledging the 
external similarities between lichens and ascomycetous fungi, asserts, 
as does Crombie, that there are too many differences between them 
to admit of their being placed together. *' The hyphaeof lichens." 
he says, " are perennial, tough, thick-walled, straight, and insoluble 
in hydrate of potassium, while the hyphae of all fungi are soft, thin- 
walled, flexuous, immediately dissolved in hydrate of potassium." 
Besides the *' Lichenian reaction " is seen in all lichens and in none 
of the fungi. Both these points are denied by many eminent lichen- 
ologists and fungologists. De Bary has found the *' Lichenian re- 
action" in several undoubted fungi, llartog, de Seynes, etc., say 
that fungal hyphae are no more soluble in hydrate of potassium than 
are lichen hypha?. 
Nylander also speaks of the ** improbability " of the lichen hyphas 
being endowed with the reason and sagacity necessary to search out 
a peculiar kind of alga3 which it may imprison and press into ser- 
vice." 1 He further urges, as does Crombie and others, that no algas 
will grow in such bare, exposed places as those chosen by most lich- 
ens. Cooke, who uses this same argument, says further that those 
lichens that do grow in low, wet places, as Collema, etc., are by 
some authors supposed to be algae themselves and therefore should 
not be used in an argument for Schwendenerism. Nylander, how- 
ever, takes an opposite view and places many of the algae of Schwen- 
dener and Bonet, etc. (such as Sirosiphon, Scytonema, Stig- nema, 
Nostoc, Trentepohlia, etc.) among the lichens, as he has found fruits 
upon them. But he finds no hyphae. From these discoveries he 
argues that even if there is parasitism, it is not that of a fungus upon 
an alga, but rather of a lichen upon a lichen. He was one of the 
first to place Cora among the lichens. 
Crombie says that finding and producing of zoospores in free 
gonidia does not prove that gonidia are identical with algae, but that 
they are only similar to them. 
The autonomists raise quite an objection as to the relative size of 
» Why is it that any parasite, either vegetable or animal, is generally limit- 
ed to but one or at most to but a few species upon which it feeds ?— Heredity, 
