258 APPLIED ECOLOGY 



vegetation would be much more valuable than a classification made 

 on any other basis. 



153. Crop Production.— The entire problem of crop production is 

 an ecological problem since it is concerned solely with the relation of 

 crop plants to the environment. Before planting the seeds of a crop 

 plant it is necessary to select a place that is ecologically suitable in 

 its climatic and soil factors, and to prepare the seed-bed in the way 

 demanded by the ecological adaptations of the plant concerned. 

 After the seeds have germinated it is necessary to know what meth- 

 ods of cultivation will make the habitat most favorable for develop- 

 ment of the plant. The problems of soil fertility are ecological 

 problems. Crop rotations are based upon the ecological relations of 

 the crop plants concerned. Thus it is readily seen that the art or 

 vocation of crop production is solely applied ecology. Crop ecology 

 is, therefore, an all-important part of agronomy and is based, of 

 course, upon general plant ecology. 



154. Symbiotic Phenomena.— The practical applications of 

 studies in symbiosis are many and varied. We have already pointed 

 out some of the applications of studies of plant communities, which 

 represent social disjunctive symbiosis, and the grazing problems that 

 we have discussed fall under antagonistic nutritive disjunctive 

 symbiosis. Pollination studies are extremely important from an 

 economic point of view. The business of honey production is based 

 entirely, of course, upon the symbiotic relation between bees and 

 flowers. The commercial production of figs in America was entirely 

 impossible until the symbiotic relation of the fig tree to a pollinating 

 insect had been studied. The successful production of vegetables 

 and fruits in greenhouses has depended in some cases upon pollina- 

 tion studies. The symbiotic relations between crop and ornamental 

 plants and disease-producing organisms are, of course, of vast im- 

 portance to man. In fact the science of plant pathology deals almost 

 solely with symbiotic phenomena. The symbiotic relation between 

 legume plants and nitrogen-fixing bacteria can scarcely be over- 

 estimated. The successful cultivation and propagation of orchids 

 has until recently depended upon a knowledge of their symbiotic 

 relation with endotrophic mycorrhizal fungi, and this is more or less 

 true also of the cultivation of blueberries and other members of the 

 heath family such as Rhododendrons and mountain laurel (Kalmia). 

 The exact relationship between ectotrophic mycorrhizal fungi and 

 their host plants, especially in the case of forest trees, is still a some- 

 what unsettled question and much work must yet be done before 



