8 BOTANY 



plants which, living in water, are passively moved about 

 by the currents of the stream. 



The fact that a plant is alive and conducts itself as a 

 living organism implies certain things. It must receive 

 suitable and sufficient nourishment; it must possess a 

 certain power of adjusting itself to its surroundings, 

 defending itself against possible dangers and over- 

 coming definite difficulties which these surroundings 

 occasion, and taking advantage of such benefits as are 

 met with in them. It must possess, to at any rate a 

 limited extent, a power of appreciating its relations to 

 such surroundings, of realising variations in certain of 

 them, such as light, moisture, and temperature, that it 

 may adapt itself accordingly. 



The second fact, that it cannot alter its position by 

 moving freely about, makes those requirements more 

 essential. It also demands that it shall be possessed of 

 such a safe attachment to its situation as shall secure 

 it an appropriate position and shall enable it to enjoy 

 undisturbed such advantages as the surroundings offer. 

 Further, it calls for a certain power of adjustment of its 

 various parts to the air above it and the earth in which 

 it is fastened, as changes in both of them are frequent 

 and sometimes violent. As the only sources of nourish- 

 ment possible to it are the air and the soil, together 

 with the water which both contain in constantly vary- 

 ing amount, its construction must be such that the same 

 parts which secure anchorage or support shall be capable 

 of securing supplies of the various materials which ulti- 

 mately become the medium of nourishment. 



A further requirement of every living organism is the 

 need of possessing the means of bearing offspring which 

 shall succeed it in the great scene of nature. To a 

 stationary organism this introduces difficulties from 

 which the readily moving animal is free, but these diffi- 

 culties have been overcome by adaptations to the habit 



