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 thallus 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 Jons son 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 hand, 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: — 
Forma 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 almost or quite solid stems and these could 
hardly be distinguished from long-stemmed L. saccharina. In this 
connection I would call attention to the specimens which Far- 
low (Marine Algse of New England, p. 93) in his description 
of L. longicruris mentions as follows: — »specimens resembling 
L. saccharina, but with hollow stipes have been collected in Long 
Island Sound. Whether really belonging to L. longicruris is doubt¬ 
ful and the subject requires farther investigations«; if the stems of 
