Distribution of the Laminariacem. 339 



The better known species are S. dermatodea (DelaPyl.), J. Ag. 

 and S. hidhosa, DelaPyl. S. dermatodea is the simpler form. Its 

 structure and development have been treated of by the writer in 

 another place. ^ The structure and development of S. bidhosa has 

 been carefully described by Barber.^ 



The first or primitive hold-fast of aS'. cJermatodea is discoidal but 

 soon two successive whorls of hapteres appear from a swelling, the 

 "rhizogen," which appears just above this primitive hold-fast. The 

 stipe is flattened and in young specimens expands gradually into 

 the blade which is covered at this period with cryptostomata. The 

 hold-fast therefore, as well as the blade and stipe are much more 

 complicated than in the species of Chorda. Yet the two genera 

 agree closely in possessing paraphyses destitute of the hyaline appen- 

 dages found in all the other genera. The relationship of /8. derma- 

 todea to S. hulbosa is much nearer than might be supposed from the 

 great difference in size and habit existing between the adult plants. 

 Young plants of the two species are very similar and the earlier 

 changes to produce the rhizogen is essentially^ the same in both. 

 Only two successive whorls of hapteres are produced in S. derma- 

 todea, however, while in S. hulbosa whorl after whorl are produced 

 and the rhizogen consequently becomes enlarged into the character- 

 istic " bulb " of the adult plant. Both species also, possess charac- 

 teristic sclerenchyma fibers in the medulla of both stipe and blade. 



Both species of ISaccorhiza very closely resemble those of Lamhi- 

 aria in general habit, but differ sufiiciently in structure to be kept in 

 a separate genus. 



Laminaria Lam'x. — The species of Laminaria are at present in 

 great confusion and it is very difficult to determine just how many 

 there are. About 28 species are usually recognized but several of 

 these are doubtful and little known. They may be separated readily 

 into two groups, the simple Laminarice of which there are about 11 

 species and the digitate Laminarice, of which there are about 17. 

 Although there are many important individual variations such as 

 the possession of a creeping rhizome-like organ as in JL. Sinclairii 

 (Harv.), Farlow, and in X. Rodriguezii, Bornet, the simple, discoidal 

 hold-fast in L. solidungida, J. Ag., the peculiar modification of the 

 base of the blade in L. radicosa, Kjellm. or even of more general 

 characters such a% the longitudinal splitting of the blade in the 



' Proc. Am. Acad, vol. xxvi, pp. 177-217, PI. 1-2, 1891, 

 2 Annals of Botany, vol. iii, p. 41, PI. 5, 1889. 



