198 



WHEKE PLANTS GROW 



that plants are often found in places which are little adapted 

 to them. See the fern growing on a brick in Fig. 69. 

 Plants must grow in unoccupied places. 



329. Not only do the seeds fall in unfavorable places, 

 but most places are already occupied. So it comes that 

 plants grow where they must, not where they will. 

 There are, of course, certain limits beyond which plants 

 cannot grow. Water lilies can thrive only in water, 

 and white oaks only on dry land, but it is seldom that 

 either the water lily or the oak finds the most congenial 

 place in which to grow. Fine large plants of the lily 

 and strong giant trees of the oak are so infrequent, as 

 compared with the whole number, that we stop to 

 admire them. 



330. Originally, plants were aquatic, as animals were. 

 Much of the earth was sea. Many plants are now aquatic, 

 and the larger number of these as alga? and their kin 

 belong to the lower or older forms of plant life. Many 

 plants of higher organization, however, as the water lilies, 

 have taken to aquatic life. True aquatic plants are those 



which always live in 

 water, and which die 

 when the water dries 



fer 





vp. They are to be 

 distinguished from 

 those which live on 

 shores or in swamps. 

 Aquatic plants may 

 be wholly immersed 

 or under water, or 

 partly e m ersed or 

 standing above the water. Most flowering aquatic plants 

 come to the surface to expand their flowers or to ripen 

 their fruits. Some aquatic plants are free- swimming , or 

 not attached to the bottom. Of this kind are some utric- 



316. The lichen grows on the hard rock. 



