in Rhodymeniales : II. Delesseriaceae. 
189 
Delesserta sinuosa, Lamx. 
This plant presents so great a general similarity in ap- 
pearance to D. sanguined , that the collector would readily 
acquiesce in its inclusion in the same genus with it. As 
D. sanguined has been appropriately called the f Dock-leaved ’ 
Delesseria^ so might this plant be called the ‘ Oak-leaved ’ 
Delesseria . In the remarkable similation of the veined ap- 
pearance of the leaf of Flowering-plants these two species 
stand out conspicuously among British Seaweeds. 
Kiitzing (’49), however, constituted for D. sinuosa the 
separate monotypic genus P hy codry s, and although Schmitz 
in his list of Floridean genera (’89) included the species in 
Delesseria , he seems later (’92) to have contemplated the 
possibility of its restoration to the position assigned to it 
by Kiitzing. 
A brief description of the macroscopic characters will 
explain this disinclination to include the species in the genus 
Delesseria. Its branches are traversed by a midrib from 
which diverge veins into the substance of the distended lamina. 
This midrib persists when the winged portion disappears, and 
gives rise by proliferation to the new phylloid branches. 
More commonly, however, a thallus-segment forks by the 
more vigorous growth of one of the lobes. Even when a 
lobe does not develop so as to form a distinct segment, its 
vein may become a strong secondary rib, from which prolifera- 
tions may arise as they do from the midrib. Again, D . 
sinuosa produces its tetrasporangia in marginal stichidia, 
like those of some species of Nitophyllum , and not along the 
sides of the midrib of the vegetative branches, or on special 
proliferating branches as in species of Delesseria. Further, 
the cystocarps are scattered in considerable numbers over 
the marginal region of the thallus-segment away from the 
midrib, while in Delesseria they usually occur one for each 
segment, and on the midrib. It is true that in the end the 
cystocarp of D. sinuosa is found to be seated on a prominent 
