ARCHER, ON PALMOGL@A MACROCOCCA. 111 
But in this genus Palmogloea it will seem evident, I think, 
upon a careful examination of the living plants, that there 
are associated forms of readily distinguishable diverse generic 
types, the most obvious common character being the per- 
vading elongate or oblong form of the cells. Amongst these 
Palmogloea-forms, then, including therein the single one 
placed under Trichodictyon, and of which I have just endea- 
voured to convey a very general conception, I believe I see five 
types. It is true that Professor De Bary* alludes to but 
two, and also referring to those two, and to the genus Penium 
(Bréb.), while he conceives they are undoubtedly separated 
by distinct characters from each other, he thinks those cha- 
racters seem to be of so slight value as that these three types 
may eventually have to be united inone genus.+ But surely 
Penium interruptum, or P. digitus, or P. closterioides, or P. 
cylindrus, and others, have little in common with Kiitzing’s 
Palmoglea-forms ; and, even admitting them all as belonging 
to the family Desmidiacez, if the generic types alluded to 
should prove constant—which, so far as we know, I should 
say they really seem to be, and as to which future research 
will be useful to decide—it would seem more advisable to retain 
them as representing three distinct genera. 
I have said that Kitzing’s plants included in Palmoglea 
seem to be separable into five types, and I shall now, one by 
one, endeavour to point them out. 
(1) Palmoglea Roemeriana (Kiitz.) seems altogether dis- 
tinct from any of the others. I have never seen it, but it 
seems to possess angulato-globose cells, combined into a flat- 
-tened frond-like expansion, growing in water. Whatever it 
be, it will, I think, be admitted that it has little affinity indeed 
with any of the others, and that it should find no place here. 
Kiitzing himself, indeed, places it under one of his subgroups, 
under the subgeneric name of Limnodictyon. 
(2) Palmoglwa minococca, var. eruginea (Kiitz.), appears to 
me to be aform referable rather to Gleeothece (Nag.){ than to 
this genus; but in Gloeothece no conjugative or other gene- 
rative process has been noticed, and I shall not dare to enter 
into any disquisition as to whether the forms included in that 
genus or their allies are or are not actually independent 
organisms—that is to say, whether they themselves represent 
the species or are merely the transitory intermediate phases 
in the development or “ alternations,” so to speak, of higher 
plants. Be that as it may, they are at least forms of more or 
* Op. cil., p. 30. 
+. Ib., p. 74. 
+ * Gattungen einzclliger Algen,’ p. 57. 
