CHAPTER VI 

 THE ANGIOSPERMS 



THE evolution of the seed marks the final step 

 in the complete adjustment of the plant or- 

 ganism to strictly terrestrial existence, and while 

 seeds undoubtedly arose independently in several 

 widely separate classes, most of these primitive seed- 

 plants have disappeared completely, or have left only 

 a few descendants, which maintain a more or less 

 precarious existence at the present time. One line 

 of seed-plants, however, has proved itself eminently 

 adapted to modern conditions, and constitutes an 

 overwhelming majority of living plants. These 

 prevailing flowering plants of the present time are 

 known as Angiosperms. In the angiosperms the 

 plant organism reaches its most perfect expression, 

 and they now dominate the land floras of all parts 

 of the world. Plastic to a degree unequaled by any 

 other plants, they have succeeded in adapting them- 

 selves to the most diverse conditions. In the burn- 

 ing deserts of the Tropics, at the utmost limits of 

 vegetation in the polar zones, and on mountain sum- 

 mits, angiosperms have made themselves at home. 

 Some have even invaded the sea, while still others 

 are inhabitants of fresh- water marshes or are sub- 

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