E e 
1900] Setchell, — The New England species of Laminaria 117 
tion of these structures in the various genera and species of the Zami- 
nariacea. 
'The final marks for distinguishing the species under each of these 
groups are varied, including arrangement cf hapteres, character of 
stipe, shape of the base of the blade, presence or absence of an intra- 
marginal series of alternate depressions and elevations, presence or 
absence of a ruffled margin, position, shape, etc., of the sori, the length 
of duration of the plant and the method of the renewing of the blade. 
'That some of these characters are of little value for specific criteria, 
seems evident to the writer and a few words in regard to each of them 
may help toward a clearer understanding of these matters. 
'The arrangement of the hapteres, the branching outgrowths from 
the lower part of the stipe, fixing the plant to the substratum, varies 
very decidedly in the same species according to the particular habitat 
and substratum. The tendency toward a whorled arrangement is the 
normal one for all the species, but in many of them it is very much 
disturbed, and only makes its appearance under exceptionally favor- 
able circumstances. The degree and regularity of the branching of 
the hapteres, too, is very variable and dependent upon the environ- 
ment. 
The character of the stipe often affords excellent means for distin- 
guishing the species of one or other of the smaller groups. Z. /ongz- 
cruris is readily to be distinguished from all other species by its 
hollow stipe; the stout and much flattened stipe of the forms of Z. 
digitata serves to distinguish this species from others of the digitate 
section; and while the length of the stipe is variable in all the species, 
the proportions existing between the length of the stipe and the length 
of the blade are often a great help in distinguishing between the 
forms. 
The shape of the blade, particularly of the basal portion, while 
often very variable in the same species, is yet a very satisfactory 
character in subdividing a species into its forms. 
The ruffles along the edges of the blade of the species of the .Szzz- 
plices group, have been used, in connection with the rows of alternate 
elevations and depressions within the ruffles, in distinguishing species 
and more often in distinguishing between the different forms or varie- 
ties of the same species, but this is a very uncertain character, since, in 
some species, at any rate, the presence or absence of these characters 
depends on the season. In Z. Agardhii and in Z. saccharina of the 
