488 LIFE-HISTORIES 
TAL BOON A SO= 
COSC 
Fic. 317.—Sea-tangle. Transverse section through the outer part of a 
stalk 2 cm. in diameter, §2, showing the darker rind (7, r) containing 
slime-canals (g, g); and the lighter interior tissue (p, p) which form the 
greater bulk. (Luerssen.) 
Fig. 318.—Bladder-wrack (Fucus vesiculosus, Wrack Family, Fucacee). 
Branch bearing air-bladders (/) and swollen tips (s) containing con- 
ceptacles. (Luerssen.)—Brown, slimy, tough seaweed, sometimes 1 m. ° 
long, growing attached to rocks, etc., between tides along the North 
Atlantic coast. 
A comparatively simple type is the thread-weed (Nemalion, 
Fig. 320). The thallus is small and with slender branches which 
grow at the apex but do not show much differentiation among the 
vegetative cells, Male gametangia (J, sp) are developed at the tips 
