DUBLIN MICROSCOPICAL CLUB, A415 
and comparable to what not unfrequently occurs in higher plants, 
to which latter view Mr. Archer would be inclined to lean. 
Dictyospherium constrictum, Archer, olim., fownd conjugated, 
and a true, though aberrant, Desmidian—Mr. Archer showed 
examples of the alga which he had previously described in these 
Minutes (‘ Quart. Journ. Micr. Science,’ vol. vi, n.s., p. 127 ; also 
‘Club Minutes,’ 22nd May, 1872, and named Dictyospherium con- 
strictum, but as he had now found it conjugated, and exhibited 
the zygospores, it was proven to be, in truth, no Dictyospherium 
(Nig.), but a veritable, though aberrant, Desmidian. Besides the 
cells being combined into a “colony” by branched stipites, much 
of the general appearance and habit would place this plant side by 
side with Cosmocladium, Bréb., as, indeed, Mr. Archer had previ- 
ously mentioned at a former meeting of the Club. But in Cosmo- 
cladium the Cosmarium-like cells are placed at the summits of the 
ramifications of a double stipes, whilst here it is single. More- 
over, this form is characterised by a certain amount of want of 
symmetry in its outline, and by the arrangement of the contents, 
both presenting points of difference from Cosmocladium or typical 
Desmidiez, thus rendering this form very singular in that family. 
The zygospore is orbicular, beset by a number of hyaline, terete, 
subacute, or very rarely slightly bifid spines; the empty mem- 
brane of the parent-cells minutely and distantly punctate. 
This form does not appear to have yet been found out of 
Ireland, the Rocky Valley, near Bray, being its head quarters. 
But as a brief “Minute”? here would only very inadequately 
convey a true picture of this species, Mr. Archer would defer a 
more minute description until he should be able to obtain fresh 
examples, but he was sorry to say that the form seemed to have 
suddenly, almost wholly, disappeared from its site, and it might 
be some time ere he could obtain specimens to enable him to 
prepare a detailed account of this interesting addition to the 
ranks of the Desmidiz. 
17th June, 1875. 
Structure of Leaves of Pinus Mertensiana and P. canadensis.— 
Dr. M‘Nab exhibited sections of the leaves of Pinus Mertensiana 
and Pinus canadensis, and pointed out that, although the leaves 
bear a very great resemblance externally, the two species are 
readily separated by characters presented by the minute structure. 
In P. canadensis no hypoderm exists, whilst in P. Wertensiana 
the hypoderm is well developed. 
Structure of Spine of Hipponoé variegata, A. Agass.—Mr. H. 
W. Mackintosh showed a transverse section of the spine of the 
foregoing. The central portion is occupied by very wide 
reticular tissue, which is surrounded by a ring of ill-defined solid 
pieces ; outside this is a zone of irregular network, which extends 
out in the form of rays to the grooves on the surface of the spines. 
Between these rays are the solid “spokes,” which dilate at in- 
VOL, XV.—NEW SER. EE 
