62 BASES AND CRITERIA. 



Comparison of the systems. — The three systems of Raunkiaer, Warming, 

 and Drude differ greatly as to manner of classification, but they are in much 

 greater harmony as to the essential basis. Drude, however, constantly uses 

 taxonomic criteria, though he is very far indeed from consistent, separating 

 monocotyls, dicotyls, and ferns sometimes into distinct types, sometimes into 

 subtypes, and then frequently uniting two of them or all three into the same 

 type or subtype. Raunkiaer ignores taxonomy altogether and Warming 

 practically does the same, with the exception of the thallophytic forms, in 

 which taxonomic form and life-form are more or less identical. The treatment 

 of aquatics, in which the impress of the habitat is marked, is very different in 

 the three cases. Raunkiaer makes helophytes and hydrophytes two types of 

 cryptophytes, coordinate with geophytes. Warming treats aquatic plants 

 as one of his six main divisions, though he considers them under ecological 

 classes or habitat-forms (136), while Drude makes water plants one of his two 

 great divisions of flowering plants and recognizes three amphibious and three 

 aquatic types. Raunkiaer uses bud-position as the primary criterion for his 

 five main groups (all flowering plants and ferns). Warming employs sys- 

 tematic criteria for two of his six divisions, ecologic for three, and physiologic 

 for one. Land-plants are divided upon the nature of the life-period into 

 monocarpic and polycarpic. Drude's first division is ecologic for aerophytes, 

 and water-plants, and systematic for mosses and thallophytes. In all three 

 systems the types and subtypes are frequently the same, except that Drude 

 usually divides the same type or subtype upon the basis of taxonomy. 



The systems of Raunkiaer and Drude are the most unlike, while Warming's 

 occupies an intermediate position. Raunkiaer's classification is much the 

 most compact and consistent, probably because he has adhered to one cri- 

 terion throughout. Because of this, and because he has given definite names 

 to practically every type, it is also much more usable. In fact, its great merit 

 lies in the possibility of using it as a sort of climatic index, while the other 

 two systems merely classify a great mass of plants in the usual static fashion. 

 As Warming points out, Raunkiaer's system has one disadvantage in that it 

 fails to take account of the growing season response (1906 : 6) and hence 

 applies to the flora and not to the vegetation of a region or country. 



Vegetation-forms. — For our purpose, much the most useful and consistent 

 view of life-forms is obtained from a single point of view, that of vegetation. 

 The development and structure of vegetation are chiefly a matter of dominants 

 and subdominants, and it is the life-forms shown by these which are of 

 paramount importance. Hence it becomes desirable to speak of them as 

 vegetation-forms, as Drude did originally, following Grisebach and Humboldt. 

 For practical purposes, it is undesirable to make a complete classification of 

 vegetation-forms and the latter is carried only so far as the demands of indi- 

 cator vegetation warrant. 



The dominance of a species depends upon the perfection of its methods of 

 increase on the one hand, and upon the success of its vegetative shoots in 

 competition on the other. While the latter is partly a matter of length of 

 shoot and rate of growth, it is chiefly one of carrying the shoots of one season 

 over to the next. A wholly consistent and usable system is possible upon the 

 basis of these three processes. It avoids the complexities and uncertain cor- 



