Tlumphrey : OBSERVATIONS ON Gigartina exasperata HARV. 603 
ity and strength. The epidermal cells throughout the entire 
plant are enveloped by a firm cellulose sheath of variable 
tuckness, from three to. ten mic. (Pl.»42, Fig. 4, ¢.) This 
cuticle is somewhat elastic, smooth and highly transparent. 
Pl. 42, Fig. 5, @ and 4, represent surface views of a portion 
of the frond, showing epidermal cells as seen through the 
overlying cuticle. By focusing, deeper cells beneath the epi- 
dermal layer may be seen. 
Beneath the epidermal cells and in connection with them are 
the pseudo-cortical cells, presenting an almost spherical outline 
and a somewhat loose though definite arrangement. These 
cells as well as the epidermal ones are densely filled with pro- 
toplasmic contents, though unlike the epidermal cells they con- 
tain no chromatophores. 
The sections of the stipe were stained with an alcoholic so- 
lution of methyl blue which gave a very satisfactory cellulose 
reaction and revealed the fact that all the cells were imbedded 
in a dense gelatinous matrix between which and the cell walls it 
is not easy to distinguish. 
Adjoining the pseudo-cortical cells and occupying the cen- 
tral region of the stipe is the pseudo-medullary area composed 
of irregularcells. Pl. 42, Fig. 3, and Pl. 42, Fig. 4, represent 
transverse and longitudinal sections of the stipe. In Pl. 42, 
Fig. 3, c, a network of somewhat filamentous cells is seen to 
be interwoven with other cells of different form forming alto- 
gether a rather loose arrangement. 
Lamina.—The general shape of the lamina is almost in- 
variably cuneate, attaining its greatest diameter a little way 
from the apex. Inall cases the frond is flat and not greater than 
three mm. in thickness, and when dry is quite translucent. 
It commonly grows from 30 to 50 cm. in length and from 6 
to 18 cm. in width, thus showing considerable variation in size. 
In shape itis quite as variable ; some fronds being branched pro- 
fusely while others show little or no branching whatever. 
New fronds arise from the base of the stipe forming at first 
somewhat club-shaped or pointed bodies, but later expand and 
assume the characteristic shape of the mature frond. (Pl. 42, 
Fig. 1.) Both sides of the frond, including the margin, are 
thickly studded with cystocarps and numerous epidermal prolif- 
erations. Near the base of the frond on each side is a small 
area totally void of proliferations. Here the frond is thicker 
