Distribution of the Laminariacece. 345 



Nereocystis^ P.&R. — There are two species of the famous "blad- 

 der-kelp " of California, the one, JST. Lutkeana^ P.&R. ranging from 

 Santa Cruz northward to Behring Straits, the other N. gigantea, 

 Aresch., extending from San Diego southward along the coast of 

 Lower California. The latter has been made the type of a new 

 genus by Areschoug,' viz: Pelagophycus\ but there seems to be no 

 adequate reason for separating it generically from N. Lutheana.'^ 



Both species agree in having a very long stipe which is slender 

 and solid at the base and broader and hollow above, while at the 

 apex it expands more or less abruptly into a large globular or pear- 

 shaped bladder upon which are borne two bunches of leaves. In 

 JSf. LiXtkeana the bunches are sessile upon the top of the bladder,' 

 while in N. gigantea the leaves are borne upon two dichotomously 

 branched stipes and are removed some distance from the bladder. 

 In N. LiXtkeana^ the leaves are sessile and each one on splitting- 

 divides to the very base or nearly to it, but in N. gigantea the leaves 

 are provided with fairly long stalks, and in fission the stipes are not 

 divided to the base, so that there results a Lessonia-X^k^^ portion. 

 The first leaf however must divide nearly to the very base of the 

 stipe in order to give rise to the two sets of branches. 



Of the four genera which make up this subtribe of the Lesson i- 

 idese, Dictyoneuron is the simplest and stands somewhat apart from 

 the other three. As regards the modification of the transition-place 

 it agrees well with the other genera, but in the details of the form 

 and markings of the blade as well as in the decumbent, rooting stipe, 

 it differs decidedly from the other three. But Lesso7iia, Postelsia 

 and Nereoeystis are very closely related indeed. The smaller forms 

 of Lessonia approximate to Postelsia and the latter in its hollow 

 stipe comes very near to Nereocystis. 



Subtribe 2. Maeroeysteae. — This subtribe contains a single genus 

 which, however, has a wider distribution than any other genus of 

 the Laminariacese. 



Macroeystis, Ag. — In the genus Macrocystis we find a single verj- 

 variable species.' While it possesses a compound frond which arises 



' Bot Notiser, p. 49, 1881, Obs. Phyc, Pt 5, p. 6. 



2 Cf. Farlow, Bull. Torrey Bot. Club, vol. xvi, p. 7, 1889. 



3 Cf. P. & R., 111. Alg., PI. 8 and 9. 



4 Cf. Hooker, Flora Antarctica, Pt. 2, p. 461. 



