458 



of two longitudinal rows on each side of the lamina which merged 

 into each other at the apex of the latter or frequently broke up 

 into several irregularly formed large and small patches; only rarely 

 and especially in the below-mentioned form, did I find a broad 

 sorus along the centre of the thailus as is to be found in typical 

 L. longicruris. 



I do not think that a regular change of leaves occurs in this 

 species at any fixed season. At any rate I did not observe it from 

 the middle of April to August, nor Jonsson from October to De- 

 cember. Specimens from these seasons did not show the least 

 indication of a regular change of leaves, the lamina being on the 

 contrary very large and well-developed with the apex generally 

 rotting away and falling off; so it is probably continually growing 

 at the base and dying away at the apex. Of course this does not 

 exclude the possibility of its growing more vigorously at some 

 seasons than at others. 



From the above description it will be seen that the typical 

 form of this species is well characterized, at least so it appears to 

 me. But , on the other hånd , in a habitat not favourable to this 

 species a form occurred which is especially difficult to distinguish 

 from certain forms of L. saccharina. I have named it: — 



Formå sacchariniformis nov. form. 



This (fig. 87) is distinguished from the main form by the lamina 

 being narrower and less waved, and by the base of the lamina 

 being frequently not cordate, but rounded or sometimes even wedge- 

 shaped; hence its habit bears much resemblance to that of L. sac- 

 charina and L. longicruris. The lamina varies in its consistency 

 from a sort of thin paper to a fairly thick parchment, and one of 

 the specimens had a distinctly chequered surface such as is fre- 

 quently to be found in L. saccharina. The lamina was usually 

 shorter than the stem. The former was destitute of muciparous 

 canals and its stem was generally distinctly hollow, but specimens 

 also occurred with al most or quite solid slems and these could 

 hardly be distinguished from long-stemmed /,. saccharina. In this 

 connection I would call attention to the specimens which F ar- 

 lo w (Marine Algæ of New England, p. 93) in his description 

 of L. longicruris mentions as follows: — »specimens resembling 

 L. saccharina, bul with hollow stipes have been collected in Long 

 Island Sound. Whether really belonging to /.. longicruris is doubl- 

 ful and the subject requires farther investigations« ; if the stems of 



