60 
THE SEAWEEDS 
Family SARGASSACEAE. 
Frond or thallus differentiated into organs. The vegetative part con- 
sists in attachment (or hold-fast), stem and branches and leaf-like organs, 
and is often provided with floats (vesicles). The reproductive part consists 
in special organs, the receptacles proper, in which the conceptacles are 
formed. The conceptacles are more usually hermaphrodite. The oogonia 
are monosporous. The receptacles sometimes occur as scarcely modified 
portions of the thallus. 
KEY TO THE GENERA. 
a. Certain segments of the frond transformed into 
separate receptacles. 
b. Receptacles, or bunches of receptacles, arising 
from the transformation of the upper part 
of proper branches. 
c. Stem abbreviated (2.5 to 5 cm.), not 
vesicular, giving off long branches. 
Leaves flat modified branches 
cc. Stem elongated, exceeding the branches in 
height. Leaves flat, marginal 
ccc. Stem elongated. Leaves stipitate, turbinate, 
confluent with the vesicle 
bb. Receptacles marginal. 
d, Receptacles marginal, several in series. 
Sargassitm 
C. Agardh. 
Carpophyllum 
Greville. 
Turfrinaria 
Lamouroux. 
e. Receptacles fringing the margin of the 
laciniae, slender, linear, monili- 
£orm Seirococcus 
Greville. 
ee. Receptacles marginal, supra-axillary, 
flat, mostly ovate-acuminate . . . . Scytothalia 
Greville. 
eld. Receptacles single, arising from trans- 
formation of an entire ramulus or 
proliferation. 
f. Vesicles distinct from other organs. 
Leaves not passing into branches Cystophora 
J. Agardh. 
