2 Rev. W. Smith on the Conjugation of 



disappeared. On the 29th of January ] 849, 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 in the 

 same pool. I have occasionally found single fronds of Closterium 

 Ehrenbergii in running water, but on all the occasions previously 

 mentioned, it has occurred in 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 (PI. 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 



