KINDS OF ASSOCIATION 15 



may be placed association with reference to substratum, to 

 the ground (occupation), and to migration: in the second be- 

 long light and water content association. It should be noted 

 that these are all actual associations in nature, and not con- 

 cepts such as the vegetation form, within which plants from 

 widely different associations may be classified. Naturally, 

 it does not follow that it is not logical or valuable to group 

 together those plants, such as hydrophytes, sciophytes, 

 hysterophytes, etc., which have a common relation to some 

 factor, but belong to different formations. ' 



Stratum association {associatio stratalis). Plants mani- 

 fest independent or dependent association with reference to 

 the stratum to which they are attached and from which they 

 derive food or support. Independent association 

 {assodatio contigua) is exhibited by those holophytic species 

 of a formation which are entirely independent of each other 

 with respect to mechanical support or nutrition. It is 

 characteristic of the greater number of the constituent 

 species of formations. Depend en t association 

 (associatio mutua) is manifested in the relation between host 

 and parasite, stratum and epiphyte, support and liane. The 

 idea here involved has long been recognized. Humboldt 

 (1806) included lianes as one of his eighteen vegetation 

 forms. DeCandoUe (1820:32) distinguished parasites and 

 false parasites, the latter growing on dead plants, or 

 attached to living plants, Schoww (1823 : 159) made a much 

 more miunte division, in 'which plantaeparasiticae radicantes 

 correspond to parasites, plantae parasiticae superAdales to 

 epiphytes, and plantae epiphytae spuriae, plantae epizoae, etc. , 

 to saprophytes. Meyen (1836:70) followed Schouw in the 

 main, but established the group epiphytes to include lichens, 

 and epiphytes in the present acceptation of the term. Drude 

 (1890 : 64, 68), recognized the four groups, arranging them 

 among vegetation forms. Warming (1895) distinguished six 

 kinds of association, parasitism, helotism, mutualism. 



' Clements, F. E. A System of Nomenclature for Phytogeography 

 Engler 31:bl 1902. 



