144 
BOTANY. 
entiation of portions of the plant-body into general repro- 
ductive organs, analogous to the floral branches of higher 
plants. The sexual 
Fic. 71. Part of a plant of 
knotted Rockweed (Asco- 
phyllum nodosum), show- 
ing the air-bladders. Nat- 
ural size. 
produced as lateral 
organs are developed upon modified 
branches, which differ more or less in 
shape and appearance from the ordi- 
nary ones. 
297. In Rockweed (Fucus) the sex- 
ual organs are found in the thickened 
ends of the lateral branches (A, Fig. 
72). They occur on the walls of 
cavities termed conceptactes, which 
are spherical, with a small opening at 
the top (B, Fig. 72). The concepta- 
cles are at first portions of the general 
surface, and afterward become de- 
pressed and walled in by the over- 
growth of the surrounding tissues; 
they are thus in reality portions of the 
general surface. 
298. The walls of the conceptacles 
are clothed with pointed hairs, which 
in some species project through the 
opening, and among these are found 
the sexual organs, which are them- 
selves, as Sachs has pointed out, 
modified hairs. The antherids are 
branches of hairs (A, Fig. 78); each 
antherid is a thin-walled cell, whose protoplasm breaks up 
into a large number of biciliate antherozoids, which escape 
by the rupture of the surrounding wall (B). Before rup- 
turing, however, the antherids detach themselves and float 
in the water with their contained antherozoids, 
