ON THE LICHEN-GONIDIA QUESTION. 
265 
Leptogium , Obryzum * the cephalodia of Stereocaulon , Nephro- 
mium , Stictina , and certain Pannarice ; 5. Stigonema , Ag., 
to Lichenosphceria Lenormandi , Born., Spilonema para - 
doxurn , Ephebe pubescens , and the cephalodia of Stereocaulon 
furcatum ; 6. Gloecapsa, Kutz, to Synalissa , Omphalaria , 
Phylliscum (as formerly shown by Schwendener), Cora, and 
certain cephalodia of Stereocaulon . As may readily be in- 
ferred from the above, there is not a different alga correspond- 
ing to each species or even genus of lichen ; for, as Bornet 
observes, a small number of the former furnish the gonidia for 
a great many different lichens. In the higher lichens, he 
acknowledges that it is difficult to see well the attachment of 
the hyphse, though in certain of the species above enumerated 
he has been able to detect the same kind of adhesion between 
the two as in the other cases. 
With reference to the vital subject of the relations of the 
hyphae to the gonidia, the author asserts that there is not the 
least evidence that the gonidia originate from the hyphae 
any more than the hyphse from the gonidia ; but that, on 
the contrary, the two are originally quite independent, and 
that their union is a subsequent event. This he illustrates 
and endeavours to prove from observations directly made upon 
various of the lichens which he thus reviews. In doing so he 
shows that while in the great majority of lichens the hypha 
envelopes the alga, forming a more or less embracing network 
around it, yet in certain cases the union is something more 
than mere contact, being a penetration by the hypha into the 
interior of the algal-cell. In such instances, e.g . in Arnoldia 
minutula, Born., the cell becomes enlarged, the wall thickens, 
the contents become colourless ; at length the wall shrivels up, 
and the gonidium finally becomes a dead membrane. In those 
cases where the algae are composed of independent cells, the 
modification which they undergo as the result of this union is 
not very marked, but in those where they are filamentous the 
alteration is much more visible, while in some other instances 
the individual cells are altered without the general appearance 
of the algal itself being very much affected. Various other 
points in connection with the relations between the hyphae 
and the gonidia are touched upon by Bornet in the course 
of his researches, which extend in all over some 60 different 
genera of lichens. Without, however, entering upon these 
minor details, suffice it to say that as the result of his investi- 
gations, he considers that he is fully warranted in establishing 
the two following propositions:—!. Every gonidium of a 
* Bornet does not seem to be aware that this genus is entirely parasitic, 
and belongs to the Pyrenocarpei. 
