CLOTHED wrrn vegetation. 



55 



Tip of one kind of rockvveed, showing 



spore and air bladders, one half 



natural size. 



bladders in the stalks and 

 the margin of its fronds 

 helping them to float. 



But not all the bladders 

 are empty, for the pimpled 

 ones contain the spores, 

 the most important part 

 of the plant. When these 

 little germ cells are let out 

 they swim in the water 

 until they collide with some 

 hard substance, where they 

 stick. They never travel 

 again ; but in due time 

 they develop into a thallus 

 that becomes another sea- 

 weed. 



A larger and more useful variety of these dark algae 

 is the kelp which grows in deeper water, but reaches up its 

 fronds on the top of a long stem to float in the swift cur- 

 rents. The roots, which always grasp on stones or shells 

 or anything solid upon the sea bottom, are not roots for 

 supplying nourishment as the roots of trees, but only for 

 holding their place. Their nourishment is absorbed from 

 the water at any part of their surface. When storms roll 

 heavy waves along the bottom at low tide, these over- 

 grown algae are torn from the 

 liottom and hurled up to the 

 beach along with millions of 

 rock weeds where men load 

 them into carts for manure. 

 For many years men have 

 been fertilizing their farms in 

 this town with seaweeds that 

 are the direct descendants 

 of the pioneer algae which 



\ sac, with spores magnified loo 

 diameters. 



