\ 
2 Rev. W. Smith on the Conjugation of 
disappeared. On the 29th of January 1849, I again, in a differ- 
ent locality, met with conjugating fronds, and on this occasion 
in great abundance and in very perfect condition. Conjugation 
was evidently but just commenced, the mucus envelope was ge- 
neral, the fronds exhibited the peculiar condition of the internal 
granular mass which betokens the approaching change, and were 
in those relative positions which, as will be seen hereafter, indi- 
cate a tendency to unite in the formation of sporangia. .A few 
days later, multitudes of individuals were found in every stage of 
conjugation, and the process continued until the beginning of 
March, towards the middle of which month few perfect fronds 
could be discovered, and the sporangia, hitherto in vast numbers, 
were fast disappearing: the mucus which held them in suspen- 
sion, and floating on the surface of the water, having become 
dissolved, they were only to be discovered upon a very careful 
search, entangled in the filaments of other plants or mixed with 
the earth at the bottom of the pool. At a later period, and in 
the locality of 1848, I found a few conjugated fronds on the 
7th of May 1849. 
The period of conjugation of this species would therefore ap- 
pear to be during the first three or four months of the year. 
M. Morren has noted it to occur in April, and again in June, re- 
marking, that probably two generations had lived in this inter- 
val. This opinion does not however seem to be borne out by the 
facts I have observed, as in no case have I been able to detect 
the plant in the same locality for more than a month or six weeks 
at one time, nor has it ever reappeared in any quantity im the 
same pool. I have occasionally tound single fronds of Clostertum 
Ehrenbergii in running water, but on all the occasions previously 
mentioned, it has occurred im clear shallow pools or marshes 
formed by springs on the open moorlands between Wareham and 
Corfe Castle. 
I proceed to notice the phenomena of conjugation as they 
successively presented themselves. The first is an alteration in 
the granular condition of the endochrome. This, from a light 
yellowish green, passes to a much darker shade, and the larger 
granules or “diaphanous vesicles” of Ralfs, which were ori- 
ginally few in number and arranged in a somewhat irregular 
longitudinal series (Pl. I. fig. 1), become exceedingly numerous 
and pervade the entire frond. While this change is about taking 
place, the fronds approach in pairs, approximating by their con- 
cave surfaces, and finally coming into such close neighbourhood 
that their inflated centres are in contact and their extremities 
slightly overlapped (fig. 2). In a short time, probably in the 
course of twenty-four hours, a remarkable change takes place 
both in the appearance and condition of the fronds ; a mass of 
