186 ARCHER, ON SPIROTAENIA. 
So marked, indeed, in appearance are the present examples, 
and, looking at the same time upon Asteridia in general as 
parasitic growths, the idea becomes suggested that there may 
be distinct and constant forms amongst them, and that collec- 
tively they ought to form a distinct genus. This suggestion 
I venture only to throw out; its confirmation or refutation 
will depend, of course, on time and on a great number of in- 
dependent observations. 
On the ConsuGATION of SPIROTHNIA CONDENSATA (Bréb.) 
and of Sprror#niA TRUNCATA (Arch.). By Witiiam 
ARCHER. 
THE two minute unicellular alge which form the subject 
of the following brief communication belong to a genus— 
Spirotenia (Bréb.)—comprising several well-marked forms. 
Most of these species are rare. In certain localities, how- 
ever, the first species now in question, Spirotenia condensata 
(Bréb.), is common; the other, Spirotenia truncata (mihi), 
belongs to the most rare, having been, so far as I am aware, 
found only by myself, and that in but one locality (“‘ Feather- 
Bed” Mountain). But it is not to be understood, as regards 
Spirotenia condensata, that any waters may present this 
pretty species, for it must be sought for in suitable situations ; 
then, indeed, it is frequently encountered. 
But often as S. condensata presents itself to notice, dis- 
tributed, as it appears to be, in Europe, and familiarised, as 
we cannot fail to be, with this the commonest and at the 
same time the most beautiful representative of its genus, 
both it and its congeners, have hitherto resolutely refused to 
reveal to us its mode of fructification or reproduction. Yet 
all the species are very constant to their characteristics, and 
one could not resist the feeling, as regards them, unlike, per- 
haps, many of the simple plants, that they must prove to be 
truly- sui generis. 
It is true, indeed, that & priori we would be justified in 
assuming that the mode of reproduction in this genus, like 
that of Spirogyra, &c., when found, would be seen to be by 
conjugation, and hence the genus has been by most authors 
referred to the Desmidiacee ; nevertheless, pending a know- 
ledge of the actual process from direct observation, the true 
position of the genus has remained hitherto in doubt. Thus 
