ECOLOGICAL 155 



had his precursor in Christian Konrad Sprengel, and Darwin's 

 interest in his Insectivorous Plants and Climbing Plants was also 

 characteristically ecological; but it is only within recent years 

 that there has been a precise study of plant-associations, such as the 

 characteristic vegetation of moorland, mountain, swamp, and 

 desert, and a determined attempt to interpret structural and func- 

 tional peculiarities as adaptive to the surroundings in the widest 

 sense. Kerner's well-known Natural History of Plants may be noted 

 as the first large treatise on Botany to place the ecological aspects 

 in the forefront. 



SURVEY. — An attempt must be made to map out Plant Ecology; 

 and that is not easy because of the manifoldness of the relations 

 involved. In his erudite Biologic der Pfianzen, Neger proposes the 

 following arrangement: Adaptations to warmth, to light, to water- 

 absorption, to water as a habitat, to the substratum or soil (edaphic), 

 to increase of mechanical stability, to other organisms, and to the 

 preservation of the species. But this is too elaborate, though less so 

 than most of those that have been suggested. We must be content 

 here with a much simpler outline of the chief problems. 



(i) Ways of dealing with the environment (both animate and 

 physical) so as to secure food-materials — including air, 

 water, salts — and so as to facilitate the utiHsation of radiant 

 energies, light and heat in particular. 



(2) Ways of securing survival against environing difficulties and 



limitations, including changes of weather and climate and 

 competition with other organisms, including parasites. 



(3) Ways of securing the continuance of the race, including, for 



instance, pollination and seed-scattering. 



(4) Ways of securing the intimate assistance of other organisms, 



notably in symbiosis, epiphytism, and cHmbing. 



While sustenance, for instance, is largely a physiological problem, 

 it becomes ecological when we study the plant's adjustments and 

 adaptations to particular environmental conditions. 



The four keywords in this simple grouping are Sustenance, 

 Struggle, Reproduction, and Partnerships. Many of the inter- 

 relations between plants and animals have been already referred to 

 in the zoological portion of this ecological section. 



SUSTENANCE. — It is convenient to begin with the plant's rela- 

 tion to the soil, from which it absorbs water and dissolved salts. 

 Typically this is effected by means of the roots, and especially by 

 the ephemeral root-hairs which grow out from the cells of the 

 younger parts of the rootlets, just behind the growing tips. 



In seaweeds the entire surface of the plant is absorptive, and there 



