104 DR. COCKS ON THE GROWTH, ETC., 



approachable by a boat, a good many specimens of Chrysymenia 

 rosea, — a plant which had never before been taken in Devon or 

 Cornwall, a few only having been gathered by Mrs. Hayden and 

 Mrs. Grattey in the year 1850 at Filey, on the Yorkshire coast. 

 In the year following the one in which Dr. Budd and myself took 

 our specimens, we found others growing in the same place ; but 

 afterwards they entirely disappeared from that habitat, though 

 many other specimens have subsequently been found in several 

 different localities, and, amongst others, growing on the mooring- 

 buoys in the Sound. 



Again, in the years 1850 and 1851 a considerable number of 

 specimens of that rather scarce plant, Ificrocladia glandulosa, were 

 washed up with other rejectamenta upon the beach under the 

 Plymouth citadel. These were all growing parasitically upon the 

 fronds of NitopJiyllum laceratum and Rhodymenia laciniata. Since 

 that time no other specimens have been taken in this neighbour- 

 hood, although the above-named plants on which they grew are 

 still found as abundantly as ever. 



A still more singular occurrence remains to be noticed, viz. that 

 of a single specimen being found of a species for which, from the 

 first moment I became a collector until then, I had been dili- 

 gently seeking, and which had also been carefully sought for, 

 many years previously, by Mr. Hore, without success. I allude to 

 Codium Bursa, a single plant of which I discovered growing on one 

 of the raooring-buoys in Plymouth Harbour ; and although at the 

 same time and subsequently I have examined all the buoys in the 

 Sound as well as in the harbour, I have never found another. 



How then are the irregularities in reference to the time of 

 appearance, as well as the disappearance of the plants I have before 

 alluded to, to be explained ? We know that the fructification of 

 the marine Algae takes place with regularity ; that is, the tetra- 

 spores when arrived at maturity burst, and the spores are libe- 

 rated, which are carried by currents to places where they attach 

 themselves to some substance, and in due time vegetate and pro- 

 duce perfect plants, similar to those from which they originated. 

 Such being the case, although many of the plants enumerated 

 in this paper have disappeared from their accustomed localities, 

 yet it appears very strange, and difficult to explain why, they 

 have not been found growing in other places, or washed on shore 

 with other rejectamenta. 



These observations will, in part, tend to show, as I have before 

 remarked, that the growth and periods of the appearance and re- 



