MESOTHNIUM, AND SPIROTANIA. 207 
characteristics of the forms themselves as of specific import- 
ance. The special characters, which, as I think, here deter- 
mine the genera, exist in the peculiar arrangement of the 
contents, combined with certain of the general characters 
previously alluded to; whilst I believe the specific characters 
reside in the peculiar form of the cell, and in minor differ- 
ences in the arrangement of the contents, and in difference of 
colour, &c., perceptible to the unassisted eye in the general 
mass or stratum. 
Again, Dr. Hicks seems to convey, because of the difficulty 
(for the reasons before stated) of assigning some of these 
forms to the particular ones described under Palmogleea by 
Kiitzing, and from there having been actually (as I conceive) 
included under that common gencric denomination five 
diverse types, that therefore “ no one algologist can tell dis- 
tinctly what is a Palmogloea, so as to be understood by any 
other algologist.”” I venture deferentially to deprecate this, 
as it appears to me much too hasty a conclusion. T[ must, in 
reply, urge that if many of the now well-established species 
formerly comprehended under the old incongruous genus 
Conferva were still referred to under the original designa- 
tions, and recent researches upon the forms alluded to mo- 
mentarily forgotten or ignored, that it is still more probable 
no one algologist could, under such circumstances, tell what 
was meant by another algologist. But if our plants be 
closely examined from their living examples, and de Bary’s 
descriptions and figures thereof carefully studied by any two 
algologists, I hardly think there will be any difficulty between 
them in understanding what the other means when; he refers 
to a Cylindrosystis, a Mesotzenium, or a Spiroteenia. 
Dr. Hicks does not see how I can find sufficient ground to 
state that the condition of a developing lichen figured by him 
is not a “ macrococca ””?—that is, as 1 am disposed to think 
more correctly designated, an ex ample of Mesotenium chlamy- 
dosporum (de Bary). I judge from the figure ; and I think, 
as I stated, because it seems to me, so far as I may venture 
to judge, to represent something at once sufficiently unlike 
both the form with which I am acquainted, as well as 
Kiitzing’s description and figures of his P. macrococca, as to 
justify me in that assumption. 
Again, as if it were to a certain extent evidence of the 
total instability of these forms, Dr. Hicks alludes to my 
being by no means certain what he means by Palmoglea 
Brébissonii, because I questioned whether the plant he has in 
view as Palmog glwa macrococca is the same as Palmella 
cylindrospora (Bréb.), considered by Mr. Ralfs as equivalent 
