488 



LIFE -HISTORIES 





Fig. 317. — Sea-taugle. Transverse section through the outer part of a 

 stalk 2 cm. in diameter, 'V'- showing the darker riud [r, r) containing 

 sUnie-canals (g. {]); and the lighter interior tissue (p, p) which form the 

 greater bulk. (Luersscn.) 



Fig. 318. — Bladder-wrack (Fucus trsirulusus, Wrack Family, Fiicdctw). 

 Branch bearing air-bladders (l) and swollen tips (s) containing con- 

 ceptacles. (Luerssen.) — Brown, slimy, tough seaweed, sometimes 1 m. 

 long, growing attached to i-ocks, etc., between tides along the North 

 Atlantic coast. 



A comparatively simple type is the thread-weed (Nenialion, 

 Fig. 320). The thallus is small and with slender branches which 

 Krow at the apex but do not sho\\' inneh differentiation amona; the 

 vegetative cells, Male ganietanf^ia (/, sp) are develojied at the tips 



