242 



ALG.E 



Falkenberg -Mitlheil. Zool. Stat. Xeapel, 1 878, p. 



531- 

 Wille — Bot. Sallfik, Stockholm, Nov. 19, 1884 (see Bot. 

 CentralbL, xxi., 1885, pp. 2%2 et seq.). \ 





>.e 



^^/ 



In so many of the Phoeosporeae the Hfe- 

 historv is at present but imperfectly known, 

 and different authors differ so widely as to the 

 best characters to be employed in classifica- 

 tion, that no attempt is here made to arrange 

 into orders all the known forms. A de- 

 scription is given only of the best-marked 

 groups. 



The Lamixariace.^ include many of the 

 largest of the brown seaweeds of both warmer 

 and colder seas ; in the southern hemisphere 

 they form dense submarine forests of gigantic 

 size, frequently making even deep water impass- 

 able for boats, and forming a home for myriads 

 of marine animals ; the individual ' fronds ' 

 sometimes attaining a length of several hundred 

 feet. The thallus is coriaceous, is not articu- 

 lated, and is usually attached to the sea-bottom 

 by rhizoids or root-like organs of attachment, 

 or less often by a discoid expansion, from 

 which springs a tough cylindrical stipe or stem, 

 the tissue of which is more or less differentiated 

 into a medullary portion, an internal and an 

 external cortical portion, and an epidermal 

 portion, the cells of which are coloured brown 

 bv phycophasin. It increases in length by 

 intercalary growth at the junction of the stipe 

 and lamina. Although most of the larger 

 species are perennial, Areschoug states that 

 even the largest species of Xereocystis (Post.) 

 are annual. In others the stem increases in 

 girth from year to year, attaining sometimes 

 the thickness of a man's thigh. In Chorda 



filum (Stackh.), one of the commonest of our 

 seaweeds, the entire thallus is cvlindrical and 



Fig. 215. Laviinariasaccliarina 

 Lmx., with rhizoids. s, por- 

 tion of frond which produces . 



zoospores (reduced \). (After whip- like, as much as lorty fect in length, 



Reinke.) 



