108 TENTH ANNQAL REPORT OF 



and the AlgfB of deep parts of the sea are to those of tidal rocks, as 

 alpine plants are to littoral ones. In both cases there is a limit to 

 the growtii of species ; each aerial species having a line above which 

 it does not vegetate, and each marine one a line beyond which it does 

 not descend. And as, at last, we find none but the least perfect lichens 

 clothing the rocks of high mountains, so in the sea beyond a moderate 

 depth are found no Algae of higher organization than the Diatomacece. 



These latter atomic plants would appear to exist in countless numbers 

 at very extraordinary depths, having been constantly brought up by the 

 lead in the deep-sea soundings recorded in Sir James Ross's Antarctic 

 voyage. But ordinary sea plants cease to vegetate in comparatively 

 shallow water, long before animal life ceases. The limits have not 

 been accurately ascertained, and are probably much exaggerated as 

 commonly given in books. 



Lamouroux speaks of ordinary Alga3 growing at 100 to 200 fathoms^ 

 but we have no exact evidence of the existence of these plants at this 

 great depth. The Macrocystis, the largest Alga known, has some- 

 times been seen vegetating in 40 fathoms {Hook. Fl. Ant. vol. 2, p. 

 464) water, while its stems not merely reached the surface, but rose at 

 an angle of 45° from the bottom, and streamed along the waves for a 

 distance certainly equal to several times the length of the "Erebus;" 

 data which, if correct, give the total length of stem at about 700 

 feet. Dr. Hooker, however, considers this an exceptional case, and 

 gives from eight to ten fathoms as the utmost depth at which sub- 

 merged seaweed vegetates in the southern temperate and Antarctic 

 ocean ; a depth which is probably much exceeded in the tropics, and 

 whicli is at least equalled by AlgfB of the north temperate zone. 



Humboldt, in his "Personal Narrative," mentions having dredged 

 a plant to which he gave the name Fugus viti/oUus, (probably a 

 Godium or Flahellaria) in water 32 fathoms deep, and remarks that, 

 notwithstanding the weakening of the light at that depth, the color 

 was of as vivid a green as in Algas growing near the surface. I 

 possess a specimen of Anadyomene stellata dredged at the depth of 20 

 fathoms, in the Gulf of Mexico, by my venerable friend the late Mr. 

 Archibald Menzies, and it is as green as specimens of the same plant 

 collected by me between tide marks at Key West, and is much more 

 luxuriant. 



Professor Edward Forbes, whose admirable report on the jEgean 

 Sea should be consulted by all persons interested in the distribution of 

 life at various depths, dredged Consiantinea reniformis, Post, and 

 Rupr. in 50 fathoms, the greatest depth perhaps on record, as accu- 

 rately observed, at which ordinary Algre vegetate. I say, ordinary 

 Alga;, for it will be remembered that Diatomacea? exist in the pro- 

 found abysses of the ocean, as far as we are acquainted with them. 



And besides these microscopic vegetables, Alga3 of a group called 

 NuUipores or Corallines {Corallinaceoi) , long confounded wi:h the 

 Zoophytes, become more numerous as other Alg?e diminish, until they 

 characterize a zone of depth where they form the whole obvious vege- 

 tation. These remarkable plants assimilate the muriate of lime of 

 seawater and form a carbonate in their tissues, which from the great 

 abundance of this deposit become stony. The less perfect NuUipores 



