66 PROCEEDINGS OF SOCIETIES. 
necting canal half-way between the two joints, and the shutting 
off thereupon of the residue of the pale granular contents re- 
maining in each parent joint, the denser central portion becoming 
the spore, and that cut off on each side eventually becoming effete 
and lost. Hence, in Mougeotia glyptosperma (de Bary) the spore 
is the actual result of the complete fusion of the entire cell-con- 
tents of the two conjugating joints—it is the true zygospore; 
whilst in Mesocarpus the ultimate spore is a daughter-cell, as it 
were, of the zygospore. Therefore, on the other hand, the present 
plant shows an affinity to Zygnema; but it is, of course, com- 
pletely distinct in the flattened band of endochrome, not doubly 
stellate, as in that genus—not to speak of the extremely different 
comparative length of the cells, which, within the limits of each, 
is constant. The complete emptying out of the conjugating cells 
in this plant imparts a peculiar smooth, almost shming appear- 
ance to the filaments, which, coupled with the curious elliptic, 
grooved, and ridged spores, gives this plant, in this state, a very 
pretty appearance. The peculiar keeled form of the spore just 
alluded to can hardly be regarded as more than of specific im- 
portance. Other forms of the genus may present themselves pos- 
sibly without this character, and the genus must rest on the 
peculiar plan of conjugation. Mr. Archer thought it was to be 
regretted that Professor de Bary had revived the name “ Mou- 
eotia” in a new sense, as it may lead to confusion, he having 
proved that Mougeotia genuflexa (Ag.) is properly to be regarded 
as a Mesocarpus. In fact, when the genus now drawn attention 
to is mentioned, in order to avoid ambiguity it must be written 
Mougeotia (de Bary, non Ag.)—Mougeotia (Agardh) being 
in part equal to Mesocarpus (Hass.), de Bary. The differential 
character of the two genera were well exemplified by the speci- 
mens exhibited, contrasted with W/esocarpus scalaris, which species, 
so far as it goes, agrees with Mougeotia glyptosperma (de Bary) 
in having an elliptic spore, and in both the longer diameter thereof 
running at right angles to the conjugating joints. But, notwith- 
standing these resemblances, no one could examine them eyen for 
a moment without at once perceiving that they were quite specifi- 
cally distinct, though they might at first sight, perhaps, be thought 
to be of the same genus. But in this regard, too, a brief inspec- 
tion would show, as above detailed, that the characters appertain- 
ing to each were of abundant importance to separate generically 
Mesocarpus (Hass.) from Mougeotia (de Bary, non Ag.). 
Mr. Archer laid on the table a number of very rare Desmidi- 
ace which he had lately been so fortunate as to encounter. The 
rarest was Stawrastrwm pungens (Bréb.), new to Ireland. This 
pretty little gem has only two localities mentioned by Ralfs, but 
it is recorded by de Brébisson at Falaise and by Bailey at New 
York. The present specimens were taken from a pool at the 
margin of “Callery Bog,” top of the “ Long Hill,” near “ Sugar- 
loaf”? mountain. The spines were finer and rather longer and not 
