VITRICOLE LICHENS AND THE SCHWENDENERIAN HYPOTHESIS. 31 
face of the glass, we have, under the microscope before our eyes, 
numerous germinations and prothalline formations, and then 
gradually advancing the beginnings of the primary glomeruli of 
the thallus (as are sufficiently well figured in 1 Tul. Mem. Inch.,’ 
t. 3, f. 3), and behold the whole process of evolution from the 
germinating spore to the perfect thallus, and at length to the for- 
mation of the perfect apothecium. All of these are seen to be 
formed of themselves — that is, by an innate power or impulsion of 
procreation, which is inherent in the spore, the only aiding materials 
being those lent by the atmosphere, especially rain water. Upon the 
very pure glassy substratum where these vital phenomena go on ; 
no trace of any Protococcus (or PI eurococcus') nor of any element 
of a heterogenous thallus is detected in the vicinity, although we 
have examined innumerable examples of such germinations in 
very favourable circumstances, especially in Lecanora galactina, 
Ach., Lecanora exigua, Ach , and Lecidea alboatra (Hoffrn.), grow- 
ing upon glass. The prothalline commencements of Lecanora 
exigua radiate dendritically around the spores, and are of a blackish 
colour, forming the hypothallus, in which minute cellulose thalline 
glomeruli are produced, presently exhibiting gonidia forming them- 
selves in the cells (as in 1 Tul. Mem.,’ l.c.) ; often also we see 
apothecia produced even in a very young plant. The same is the 
case with the beginnings of Lecanora galactina ;* but here the 
hypothallus is white, consisting of white byssine appressed fila- 
ments, laterally apposite and contiguous. All these hypothalli 
are very closely agglutinated to the glass ; and there are no traces 
whatever of any Protococci in connection with them.” 
These observations of themselves, in connection with Yitricole 
Lichens (which, in this country, we have only observed on broken 
pieces of bottles on garden wall tops, chiefly in Scotland), are 
amply sufficient to show how untenable is the Schwendenerian 
hypothesis, which, in the concluding words of Nylander’s paper, is 
thus “ reduced to the nothingness from which it ought never to 
have emerged.” J. M. Crombie. 
PREPARATIONS OF LICHENS. 
If the Schwendener theory of the dual nature of Lichens has 
done no other service, it has at least been the means of attracting 
attention to a sorely neglected group of cryptogamic plants, con- 
cerning which the majority, even of educated persons, were in pro- 
found ignorance. Like all other branches of Natural History, 
Lichens, as now understood through the medium of our improved 
microscopes, are very different to what they were fifty years ago. 
There are also other reasons which have given Lichenology an 
impetus forward in Britain, and chiefly the increased facilities for 
* This I can entirely corroborate from my own observations on this species, 
as growing on mortar in the north suburbs of London. — J. M. C. 
