No. 44.] 
[June, 1879. 
dmilba, 
A QUARTERLY RECORD OF CRYPTOGAMIC BOTANY 
AND ITS LITERATURE. 
THE DUAL LICHEN HYPOTHESIS. 
CContinued from Page 108.J 
Are Gonidia a part of the Lichen-structure ? — The thalli ol 
Lichens enclose within them peculiar cellules, forming a sub-corticaf 
layer, which are sub-globose, of a greenish colour, and to these the 
name of gonidia has been given. They frequently burst through, 
and appear on the surface, in the form of powdery masses. The 
lichenologist believes, and as he thinks has good reason for believ- 
ing, that they form part of the plant itself. One says, “ They 
may be regarded as intermediate in function between the vegeta- 
tive and reproductive cell, assuming the offices and partaking of the 
characters of both.”* The justly celebrated Tulasne considered 
them to be parts of the Lichen, and also to perform important 
functions. On the other hand, the theorists contend that they are 
no part of the plant, but that they are a form of Algae, upon 
which the residue of the Lichen is parasitic. The grounds of the 
belief are supposititious, and the proof is still defective. 
In the first place, it is argued that they are free cells, resembling 
in size, form, and colour certain low forms of unicellular Algae, and 
hence, as they are out of place in Lichens, they must be unicellular 
Algae. 
Any one who has had any experience amongst the low forms of 
of vegetable life, in which the organism consists of a single cell, 
are exceedingly well aware that it is almost an impossibility, from 
the observation of these cells, to arrive at any satisfactory conclu- 
sion as to what they are, and what their ultimate development may 
be. Let them compare, if they please, what are known to be the 
earliest stages of Mosses and Algas with the gonidia of Lichens, 
and draw up characteristic diagnoses if they can. All are globose 
cells containing a greenish protoplasm, and about equal in size. By 
what occult power can the theorists distinguish that which, it is 
admitted, they cannot describe ? Yet the best and most experi- 
enced Algalogists affirm that of all these forms the gonidia of 
Lichens are the most distinct and permanent in their character. 
* Lindsay, “ Loc. Cit.,” p. 41. 
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