‘ARCHER, ON PALMOGL@A MACROCOCCA. 119 
present themselves, as I have endeavoured to show. It 
may indeed be quite probable that some of his forms are 
described as distinct upon characters too trivial; thus I 
would be disposed to suggest, altogether conjecturally, that 
his P. vesiculosa and P. macrococca may be possibly identical 
—P. lurida and P. rupestris—P. protuberans and P. ma- 
crococca ; but in the main, so far as I can judge, the forms 
generally referred to by him to this genus seem to be 
distinct. On the other hand, I fancy that, as might be 
expected, a few forms appertaining to Mesotznium, described 
by Nageli and De Bary, do not occur at all in ‘Species 
Algarum.’ 
In thus expressing an opinion as to the actuality and dis- 
tinctness of these species, which I would wish to do very far 
from dogmatically, I am not unmindful of the statements 
made by writers as to the diamorphosis of these forms—that 
is, as to their being more or less transitory conditions of 
higher plants. But it, indeed, appears to me, that anything 
as yet adduced in support of the transition of a true Palmo- 
gloea—that is to say, of either a true Spirotenia, Cylindro- 
cystis, or Mesotzenium—into or from any other plant is by 
no means so conclusive as regards, an actual diamorphosis, as 
are De Bary’s observations on their development from one 
generation to another, through germination of the spore 
formed by conjugation, apparently decisive as regards their 
perpetuated identity and constancy. Kiitzing, indeed, speaks 
of a transition of his P. protuberans into Scytonema,* and of 
his P. vesiculosa into a Zygogonium ; but, very deferentially, 
1 think his statements and figures are too meagre, in these 
cases, to prevent great doubt as to the correctness of his con- 
clusions ; besides, it is possible, indeed, that his plants thus 
-ealled may not, strictly speaking, belong at all here. Again, 
Dr. Hicks + draws attention to an elongate form of cell no- 
ticed by him during the development of lichen-gonidia, and 
which he considers nothing but a “ Palmoglea;” conse- 
quently, he seems to come to the conclusion that all the 
Palmogleea-forms are but conditions in the growth of the 
gonidia of lichens. Far be it from me to doubt the accuracy 
of Dr. Hicks’ very valuable and remarkable* observations ; 
but, at least, so far as the forms of Cylindrocystis and Meso- 
teenium (by whatever names they may pass) are concerned, I 
would suggestively put it, that here, as elsewhere, resemblance 
may by no means necessarily constitute identity. We are 
not now so much astonished as formerly at remarkable cases 
* © Phycologia Generalis,’ p. 178. 
+ ‘Quart. Journ. of Mic. Science,’ vol. ii, n. s., pp. 17 and 20. 
