2 
K. MI Y ABE 
A. Paraphyses with the apical walls not markedly thicker than the lateral ones 
(1) . Stipe wanting ; blade filiform, hollow, the cavity separated by dia- 
phragms into many chambers (1) Chordeae 
1. Sporangial sori cover the whole surface of the blade except the 
basal portion 1. Chorda 
B. Paraphyses with markedly thickened apical walls which are mucilaginous 
in substance and laterally connected with each other ; distinction between 
stipe and blade portions clear 
(2) . Blade dotted on surfaces with minute depressions which have tufts 
of hairs or cryptostomata ; mucilage lacunae absent; a centrally located 
midrib present; thin membranous in the marginal portions 
(2) Alarieae 
2. Stipe giving rise on both sides of its upper portion to many leaflets 
which are covered with sporangial sori on both surfaces ; blade at 
the top of the stipe undivided 2. Alaria 
3. Stipe giving rise on both sides of its lower portion to a strongly 
undulate wing which is covered with sporangial sori on both 
surfaces ; blade at the top of the stipe divided deeply into pinnate 
segments 3. Undaria 
(3) . Blade with numerous small perforations ; mucilage lacunae and crypto- 
stomata absent (3) Agareae 
4. Blade simple, a midrib present 4. Agarum 
5. Blade terminating each branch of the repeatedly divided stipe, inrolled 
at the lower margins, midrib absent .... 5. Thalassiophyllum 
(4'. Blade with no perforation, mucilage lacunae usually present but some- 
times absent, cryptostomata absent (4) Laminarieae 
6. Stipe undivided ; blade simple, entire and more or less ruffled on 
the margins, or split palmately into several segments, longitudinal 
ribs absent; mucilage lacunae present or absent . . 6. Laminaria 
7. Blade giving rise to entire or deeply lobed leaflets on the margins, 
mucilage lacunae present, longitudinal ribs absent . . 7. Ecklonia 
8. Blade with five longitudinal ribs, mucilage lacunae absent .... 
8. Costaria 
9. Stipe branching dichotomously, each branch bearing a simple terminal 
blade ; blade with an auriculate outgrowth on each side of the lower 
margin, the outgrowth becomes the meristem which gives rise to 
a stipe and blade in the succeeding year; mucilage lacunae present 
9. Arthrothamnus 
