HARDWICKE'S SCEN CE-GO S SIP. 



241 



ON THE lEEEGULxiEITY OP APPEAEANCE OF MAEL\E 

 AWM ON THE BEITISH COASTS. 



No. 2. 



By W. H. GRATTANN. 



i^ N the September 

 number of this 

 Journal I wrote 

 on the appear- 

 ance and disap- 

 pearance of cer- 

 tain species of 

 marine algse on 

 parts of the British 

 I am now about to 

 the result of my obser- 

 vations on the disappear- 

 ance of some rare species 

 of alga; from the localities in 

 which I found them last 

 season, and of the appear- 

 ance of some other unlooked- 

 for species in the situations 

 so lately vacated by their pre- 

 decessors. 

 On one of the rocky emi- 

 t round the Corbon's Head, in Torbay, 

 deep round hole, which, at the recess of 

 the tide, is always left full of sea-water, and in this 

 rocky hollow many species of green, olive, and red 

 seaweeds have, season after season, found a sheltered 

 place of growth. This is the third season that I 

 have paid periodical visits to the shores around Tor- 

 quay, and as regards the rock-pool just spoken of, 

 which I have looked upon as a nursery for rare alga;, 

 I have wondered that the same species of plants 

 should not be found there two seasons consecutively. 

 Last summer, as stated in my former description of 

 this very pool, I found the rare green plant Bryopsis 

 hjpnoides growing in profusion, and although I 

 helped myself pretty liberally, I left many beautiful 

 fronds of it there; and upon many subsequent visits, 

 I watched the gradual breaking-up of the pretty 

 No. 107. 



nences ju: 

 th^re is a 



green branches, and even the final disappearance of 

 the plant, and as 1 felt pretty sure that no other 

 collector had disturbed it, I waited with a botanist's 

 patience and interest for the return of spring, hoping 

 to find a goodly supply of this rare and beautiful 

 Chlorosperm. 



Although this plant is a summer annual, it ought, 

 in a sheltered place, to have made its appearance by 

 the end of May at the latest ; but I regret having 

 merely to record ray disappointment, for there was 

 not a scrap of it in the place. If the species were 

 perennial, we should look for young plants springing 

 up from the old stems, and should most probably find 

 them as the season advanced ; but this plant is propa- 

 gated by zoospores or active granules, which are, in 

 fact, nothing more than a transformation of the endo- 

 chrome, or colouring matter of the tubular cells of 

 the plant ; and as upon their emission fi'om the 

 parent cells they would naturally be swilled out of 

 the rock -pool by the in-flowing tide, and would be 

 very unlikely to be brought back again to the same 

 place, I think it not improbable that this may 

 account for the absence this season of Bryopnls 

 hjpnoides. If this be so, the same tides which carry 

 away the spores of some seaweeds to distant locil- 

 ities, may also bring the fruit of others; and thus, 

 while I regretted the loss of one rare plant in the 

 Torbay rock-pool, I was rejoiced to fiud another 

 which I had not previously seen in that locality, nor 

 indeed in any other situation around Torquay. This 

 was the pretty olive plant Striaria attenuata. It 

 was growing on the old stumps of Ceramium ruhruni, 

 which fringed the sides of the rock-pool. In my 

 former paper I described another rock-pool, which 

 is merely a wide^ hollow basin on a projecting ledge 

 of rock, far up one of those cavernous openings 

 round the Corbon's Head, in which I found, last 

 season, some lovely specimens of Bryopsis hypno'ides. 



M 



