54 The Plant World. 



in root-systems may be seen, and the observer will avoid many 

 pitfalls by remembering that climatic effects are not necessarily 

 climatic adjustments or adaptations. 



We do find however, that the plants of the desert, of the 

 swamp and of the mountain top are so well fitted for these places 

 as to thrive and survive although by no means so perfectly as 

 might be supposed. Some of them grow much better under cir- 

 cumstances wholly new to them . The fact remains, however, 

 that some specialized and fitting characters are to be recognized. 



One of the most pressing problems in evolution at the pres- 

 ent time is to determine how these and other characters were de- 

 veloped or acquired. Does the plant grown in the desert for a 

 few generations carry xerophytic features when removed to a 

 new habitat or not? 



If a general view be taken of the available information 

 some interesting facts will be discerned, obtained by the 

 operations of the horticulturist, the agriculturist, and the 

 breeder, as to the behavior of crops, plants and domestic 

 animals, when transferred from one habitat to another. 

 The greater part of such data is the result of obser- 

 vations which do not comply with the ordinary requirements 

 in the avoidance of error so that strict comparisons as to the be- 

 havior of organisms under the conditions of various habitats 

 are impossible. A consideration of this literature yields many 

 suggestions for experimental research and the simple generaliza- 

 tion that the direct effects of climatic complexes on the seasonal 

 cycle, and upon color, or structural features of the individual, 

 may be repeated or carried over two or three generations, in 

 a habitat where the specific causal combinations are lacking. 

 This is the available total knowledge furnished us by the eco- 

 nomic operations, and by the introduction operations of botani- 

 cal gardens and plantations. 



The awakening of interest in the matter has led to the 

 organization of a great number of experimental researches, 

 during the last decade, and some of the results announced are 

 suggestive and even decisive in some cases. 



The recent work of Buchanan with Streptcocus lacticus yields 

 the conclusion that phases of fluctuating variations in the bac- 

 teria induced by cultures may not be fixed, and are not trans- 

 missible, which is in accord with the main body of evidence upon 



