26 



OUTLINES OF PLANT LIFE. 



pairs of oval bladdery swellings, which, by the gases they con- 

 tain, give greater buoyancy to the plants in the water. 



Fig. 27. — Upper part of a plant of Fucus vesicn.osus. r, midrib of thallus ; /, 

 bladders ; s, swollen tips covered by numerous elevations, in each of which is a pit 

 which contains many sex-organs. Two thirds natural size. — After Luerssen. 



35. Growing point. — The very tip of each growing branch 

 is notched and at the bottom of the notch is a group of cells 

 which by division produce all the parts of the thallus. This 



