Mr. J. Ralfs on the British Desmidiece. 13 
is of an opake green. The latter if kept in water for a few days 
spontaneously separates into fragments ; G. mucosum, although 
treated in the same manner for weeks, has not separated into 
fragments sufficiently small to enable me to obtain a transverse 
view. Iam therefore unable to say whether the endochrome in 
that aspect appears stellate, as in G. dissiliens. 
Under the microscope G. mucosum may be known by the joints 
not appearing crenate and by the endochrome being in a single 
patch, or if divided, the joints are longer than in G. dissiliens: Its 
mucous sheath is with difficulty detected, and when seen will be 
found to extend on each side twice the breadth of the coloured 
filament ; whereas in G. dissiliens the mucous sheath is, except in 
old specimens, detected without difficulty. 
This is a remarkable plant, and differs in many respects from 
the other Desmidiee ; indeed so much so, that I had some doubts 
whether it would be correctly placed in this family; but as the 
Rev. M. J. Berkeley, as well as every other algological friend 
whose opinion [ solicited, considers that its place must be in the 
same genus with the preceding species, I have described it here. 
The joints seem to be in pairs, and a single one is consequently 
unsymmetrical. , 
G. mucosum agrees with the other Desmidiee in its capability 
of being kept a long time without undergoimg decomposition. 
I was indebted to Mr. Hassall for the information that the 
plant under consideration was the Conferva mucosa, Dillw., as 
also for an opportunity of examining a foreign specimen under 
that name from the herbarium of Dr. Greville. 
1 have since been able to compare our plant with a portion of 
an Irish specimen of Conferva mucosa presented to me by Mr. 
Borrer, who received it from SirW. J. Hooker. From the latter 
I learn that this was an original specimen from Miss Hutchins. 
Sir W. J. Hooker has also presented me with an Appin specimen 
collected by Capt. Carmichael. All these are identical with the 
present plant. 
Prate III. fig. 6. Gleoprium mucosum : a, portion of a filament much 
magnified to show the bifid projections; 4, less magnified to show the 
breadth of the sheath. 
Sp £RozosMaA, Corda. 
Filaments gelatinous, plane, fragile ; joints closely united by 
means of glandular processes, and deeply divided on each side, 
thus forming two segments and giving a pinnatifid appearance 
to the filament. 
The filaments are pale green, gelatinous, simple, plane, have a 
pinnatifid appearance from the division of the joints into two 
segments, are fragile, and finally separate into single joints. I 
