Yendo. — On the Mucilage Glands of Undaria . 615 
Number of Glands in a Pinnule at the Transitional Region. 
Of a plant about 1 1 cm. high. 
I. 
II. 
III. 
Middle part 
30 
25 
26 
Marginal part 
59 
56 
70 
Of a plant about 30 cm. high. 
Very small ligule, hence middle 
and marginal together . . . 
21 
16 
20 
Of an adult sporophyllous plant, about 43 cm. 
high. 
Middle part 
6 
0 
4 
Marginal part 
J 3 
14 
21 
Number of Glands in Young and Old Pinnules of a Sporophyllous 
Plant about 43 cm. 
HIGH. 
Young Pinnule. 
Old Pinnule. 
I. II. III. 
L 
II. 
III. 
Middle Part 0 1 1 7 
10 
7 
5 
Marginal part 20 16 21 
13 
l 9 
27 
These spots are narrow spaces, mostly circular in surface view, with a 
diameter varying from 10 to 15 \x. Some are elliptical or ovate, measuring 
10-15 1 u in the minor axis and 20-40 j u in the major axis. In the younger 
pinnules which are found near the transitional region of a frond they are 
much smaller, often not exceeding twice the size of an epidermal cell. Those 
found in the rachis, though rather rarely, are narrow and longitudinally 
stretched. Before going further, a brief description of the structure of a 
young part of the lamina of Undaria will be necessary, as nothing has ever 
been reported concerning the matter. There are many interesting points to 
be considered in the morphology of Undaria. Description in detail may 
undoubtedly contribute various new facts to the knowledge of Laminaria- 
ceae. But I have to confine myself in this paper to remarking on the 
points which directly concern the subject under consideration. 
In the essential characters the structure of a young part of the 
lamina of Undaria is similar to that of the rest of Laminariaceae. 1 The 
epidermal layers are built up of a single stratum of elliptical cells with 
the major axes perpendicular to the surface of the frond. The cortex is 
built up of parenchymatous cells disposed in one or several irregular layers. 
The cortical cells, which are directly in contact with the epidermal layer, 
are angulate-polygonal and closely fit on to the inner side of the epidermal 
layer. In the transitional region the epidermal cells are nearly isodiametric 
and have a similar appearance to the contiguous cortical cells (PI. XLVIII, 
Fig. 8). Both are, however, easily distinguished one from the other by the 
contents and future mode of development (Fig. 12). The inner cortical cells 
vary in shape from spherical to elongated-elliptical, and are arranged loosely 
and irregularly. The medullary portion between the two strata of the cortical 
1 Cf. Wille : Bidrag til Algernes Physiologiske Anatomi. K. Svenska Vet. Akad. Handlingar 21. 
No. 12. 1885. Rosenthal: Zur Kenntnis von Macrocystis und Thalassiophyllum , Flora, 1890, and 
other papers. 
