428 Mr Eattray on the Distribution of 



growth in Plocamium coccineum, Polysiphonia urceolata, 

 CallWiamnion arbuscula aiid many others tend to the same 

 result. 



From time to time experiments and observations have 

 been made on the rapidity of growtli and of distribution 

 at the marine floating laboratory of this Station, with the 

 view of procuring some data on the facility with which 

 the different species are capable of extending their range 

 and of accommodating themselves to changing conditions of 

 environment. It has already been noted that for the most 

 part hard mammillated basaltic rocks or boulders are 

 avoided by most species of algge. If, however, the smooth 

 and hard surface be more or less protected from the direct 

 force of impact of waves, and be sufficiently shaded, as, for 

 example, in the case of some of the deeper pot-holes* in 

 the vicinity of Earlsferry and elsewhere, it very often 

 bears an abundant crop, sometimes of the most delicate 

 species of Ceramics, Callithamnicc, and Polysiplionice, as well 

 as of larger forms (e.g,, Fuci, Laminarice, &c.). This is, 

 of course, readily accounted for by the fact that the 

 irregularities of the rock, though in themselves minute, 

 are yet very large in relation to the very small size of the 

 spores that seek a lodgment in them ; while in other cases 

 the settling of various forms of brackish water or shore 

 Diatoms, such as species of Podosplienia, Rliipidophora, 

 Synedra, and the commingling of Naviculce, Pinuularice, 

 and Pleurosigmata with these, very rapidly form a nidus 

 on which algoid spores readily settle and germinate. I 

 have found this to be the case with round boulders which 

 had not been disturbed by storms for some time in the 

 immediate vicinity of the Marine Station, as well as on 

 others examined from Inchcolm, Inchkeith, Fidra, and the 

 May Islands, and it has been readily proved by sinking a 



* In a single pot-hole, about 6 feet deep and from 2 to 3 feet in diameter, 

 examined for the first time by m)'self at Kincraig, near Earlsferry, during 

 August 1884, beautifiil growths of Polysqjkonia parasitica, Callitliamnion 

 gracillima, C. roseum, &c., were procured at a depth of about 3 feet from the 

 surface. The smooth margins of the hole were completely coated by a rich 

 growth from top to bottom, where delicate fronds of Laminaria saccharvna had 

 reached a considerable size. At a somewhat later period Mr George W. Traill, 

 to whom I .showed the pool, examined it more minutely, scraping off the 

 deeper forms by the delicate application of a yierforated spoon applied to the 

 end of a long stick, with the result that 68 diJEFerent species were determined 

 in it. 



