SCIENTIFIC IX TERES T 



403 



He studies, too, the increasing complexity of plants 

 from the simple, one-celled plants dependent upon water 

 for existence up through the plants which are becom- 

 ing accustomed to living ou land, and finally to the 

 which have complex: systems and complex Sowers. He 

 finds that all are related, and the more be Learns about 

 them, the more interesting does he find their relationshi] 

 He is interested in seeing how the changfe from water to 

 land calls forth changes 

 in structure to fit the 

 new environment ; how 

 in land plants, each one 

 has adapted itself in 

 form, size, arrangement 

 of leaves, and so on, to 

 make the best possible 

 use of the air and water 

 which it is able to pro- 

 cure. 



In trying to find the 

 causes of such varia- 

 tions of plants the 

 scientist performs many 

 experiments, often upon 

 the smallest plant, for size and complexity arc no Indication 

 of the interest which may center in a plant structure. Bac- 

 teria, for instance, which are the simplest and smallest of all 

 plants, are being st udied more to-day than any of the others. 



Every year adds to our knowledge of the nature of 

 plants, their relations to each other and to man. Besides 

 these relations due to their surroundings, plants bear I 

 wards each other the relation of dependence and inde- 

 pendence, which we have discussed under parasitism and 

 symbiosis. 



Figure 441. — Calla. 



From an X-ray photograph. One of 

 the new ways of studying plants. 



