No. 512] PRESENT PROBLEMS IN PLANT ECOLOGY 



scientific plant-breeding methods and been shown to con 

 sist of an elementary species or variety. Too much in- 

 sistence can not be placed on this point, The use of 

 homogeneous material is an indispensable prerequisite. 



If the experiments are to contribute to the better under- 

 standing of the greater vegetation units the experiment 

 stations will need to be critically located. 



Probably the most promising field for experimentation 

 at the present time is the investigation of the processes 

 of vegetation. There are so many vague notions and 

 dogmatic statements regarding the processes of competi- 

 tion, migration, adjustment, etc., in relation to the cli- 

 matic factors, that the rewards for pioneer work will be 

 ample. Here again the methods and materials must be 

 carefully considered. In certain of these problems pedi- 

 greed (or better perhaps standardized) plants will give 

 far more definite conclusions than those whose composi- 

 tion is unknown. In others, the more nearly we approach 

 actual habitat conditions and investigate actual habitat 

 processes, the more useful will be the results. 



Experiments thus guarded may lead not only to a better 

 understanding of vegetation, but they will also contribute 

 to the science of evolution. If the methods used will bear 

 inspection both from the standpoint of the process of 

 heredity and from the processes of vegetation, natural 

 selection and adaptation may be resolved into processes 

 of more definite meaning. 



The recognition of the importance of the results of 

 ecological investigations in the practice of agriculture, 

 horticulture and forestry has added much to then- in- 

 trinsic interest. Some of the problems are perhaps »e- 

 yond the reach of the individual worker. ^Fortunately 

 there are several institutions in the I mte.l State- within 

 whose scope these problems lie. That they have alivad\ 

 begun the publication of contributions to this field is the 

 best evidence that both the larger and the smaller prob- 

 lems of the climatic relations of vegetation will be more 

 adequately studied in the near future. 



