346 



THAT'S IT; 



The best localities in which to search for the 

 smaller and more interesting specimens of alga?, 

 are those in which there are the greatest number 

 of rock-pools, of moderate extent, with perpen- 

 dicular sides, and a depth varying from one to 

 three feet. Pools of this character, though 

 situated near high- water mark, so as to com- 

 municate with the sea only when the tide is 

 near its height, often produce all the species 

 which are considered to be characteristic of 

 extreme low- water mark. Their depth is suffi- 

 cient to keep the water at a tolerably even 

 temperature, and their steep sides afford that 

 shade which the more delicate sea weeds re- 

 quire. Although the roots of sea weeds are 

 little concerned in their active growth, the 

 character of marine vegetation is greatly varied 

 by the outward form of the rocky masses. 

 Thus, on a shore composed of granite rocks, 

 where the masses are rounded and smooth, with 

 few interstices or cavities in which water will 

 constantly lie, and presenting to the waves 

 sloping ridges, along which the water freely 

 runs up and down, very few species, and those 

 only of the coarser kinds, are commonly to be 

 met with.* 



The lacerated Nitophyllum, 10, 

 is another of the red group, its 

 fronds being irregularly divided. 

 It is very frequently met with on 

 10 



1158. 



rocky coasts, growing from a 

 minute discoid base, from which 

 it is frequently broken away by 

 the waves. The whole plant is 

 in general very thin and delicate, 



* Harvey's Sea Side Book. 



of a pale pinkish red, varying to 

 reddish brown. The lower part of 

 the frond is always more or less dis- 

 tinctly marked with parallel, inter- 

 branching dark veins, originating 

 at the base, and generally vanish- 

 ing at the length of two or three 

 inches, but sometimes extending 

 even into the branches. The 

 species is exceedingly variable 

 in reference to the breadth and 

 lacerations of the frond. 



Respecting the three distinguishing colours 

 of algae, Dr. Cocks observes, that the grass- 

 green colour is characteristic of those found in 

 fresh water, or in very shallow parts of the sea, 

 along the shores, generally above half- tide level, 

 and is rarely seen in those plants which grow 

 at any great depth. But to this rule there are 

 exceptions sufficiently numerous to forbid our 

 assigning the prevalence of fhis colour alto- 

 gether to shallowness of water. 



The olivaceous brown, or olive-green series, is 

 almost entirely confined to marine species, and 

 is, in the main, characteristic of those that 

 grow at half- tide level ; but it frequently occurs 

 at greater depths, in which case it is very dark, 

 and passes into brown, or almost black. 



The red series, also, is almost exclusively 

 marine, and reaches its maximum in deep water, 

 though some varieties occur at half-tide level. 

 When above this, they assume either purple, 

 orange, or yellow tints, and sometimes even a 

 cast of green. They are, however, very rarely 

 pure red much within the range of extreme 

 low-water mark, higher than which many of 

 the more delicate species will not vegetate ; and 

 those that do exist, degenerate in form as well 

 as in colour, as they recede from it. 



There is much difficulty in 

 exhibiting by small engravings 

 the true portraits of sea weeds, 

 because the forms of the most 

 interesting specimens are minute, 

 and more particularly the details 

 are such as can only be observed 

 by attentive examination, aided, 

 in some cases, by the microscope, 

 or by magnifying glasses. We 

 may, however, point out a few 

 additional matters, which the 

 excursionist to the sea shore 

 will do well to observe : — 



Of all the aJgce the common bladder wrack, 

 which has a double series of air cells in the 

 fronds, is the most common. This plant, with 



