110 ARCHER, ON PALMOGL@A MACROCOCCA, 
vate or oblong form of the cells. As I should be disposed 
to understand it, putting aside his Palmoglea Roemeriana, 
Kiitzing must have established his genus Palmogloa for the 
reception of, and meant it to include, all those Palmellaceous 
Algze (except the one species forming his genus Trichodictyon, 
separated from his Palmogloea with little reason) possessing 
oblong, cylindrical, or elliptic cells, with granular contents, 
each cell possessing only a single simple, special, mucous coat 
not persistently included coat within coat, the whole becoming 
confluent into an indeterminate gelatinous stratum of greater 
or less density or tenuity. Itis true that, of course, im the 
specific characters and diagnosis of subgroups, the elongate 
form of the cells is alluded to, but I do not think a character 
so obviously generic should have been left to be sought for 
amongst the specific. But the fact of Roemeriana being 
included in the genus compelled him to omit this character 
from the diagnosis, 
It is, indeed, with much diffidence that I venture to suggest 
that Kiitzing’s three subdivisions of his genus are founded 
upon wholly unreliable distinctions. These distinctions in 
regard to the two principal subdivisions, P. Roemeriana form- 
ing the third, are based, so far, indeed, as I can judge, merely 
on the comparative density or tenuity of the gelatinous 
“matrix,” or, in other words, the supposed greater or less 
readiness with which the special mucous investments of the 
cells remain individually defined, or become confluent with 
each other, thus rendering the “ loculi’’ (Kiitz.) more or less 
noticeable, or not at all perceptible. These distinctions seem 
to be by no means of the constancy requisite for usefully 
available characters ; indeed, as A. Braun* well observes, of 
so little value are they as to render it doubtful in which sec- 
tion we are to seek a particular species. The remark was 
made especially in regard to a plant named by him, as most 
approaching to truth, Palmoglea macrococca (Kiitz.); but I 
venture to think that the plant meant by A. Braun was not 
that so named by Kiitzing, nor, indeed, probably any de- 
scribed by that celebrated author. Indeed, the degree of 
moisture of the situation in which these plants grow seems 
to exercise a considerable influence on the consistence of the 
common gelatinous stratum. A mass of one of these species 
in drying assumes a firmness and a somewhat elastic tenacity 
before shrivelling up. In those species which grow wholly in 
water the gelatine i is of considerable tenuity, and the cells 
sometimes even live free. 
- ‘Rejuvenescence in Nature,’ translated for the Ray Society, 1853, 
p. 327. 
