64 . FORREST SHREVE 



bility that further physiological exploration may discover in 

 other plants equally great departures from the classic types of 

 respiration, transpiration and water intake. 



This is by no means the first time that an intensive physio- 

 logical study of individual species has been urged as the only 

 direct and certain road to a better understanding of plant dis- 

 tribution. The fact has been appreciated by many ecologists 

 and physiologists and has been particularly emphasised by 

 Ganong. Our interest in the individual species had its com- 

 mencement, as have so many things in plant geography, with 

 the observations of Humboldt on the role which different types 

 of plants play in determining the physiognomy of j^he vegeta- 

 tion. Beginning with Humboldt's life-forms we have had many 

 schemes for the rough classification of plants according to their 

 size, form and gross anatomy. These schemes, propounded by 

 Grisebach, Warming, Reiter, Raunkiar, and Drude, constitute a 

 series of attempts to group plants according to their gross ana- 

 tomical and physiological characteristics. Among these classi- 

 fications of growth forms, life forms, or vegetation types, as they 

 have been variously called, the more recent sympodial ones are 

 a decided improvement over the older simple ones, and that of 

 Drude, set forth in his recent Oekologie der Pfianzen is by far 

 the best of them. These systems are of interest to us because 

 they represent the crude beginnings of an attempt to construct 

 a physiological classification of plants. The recent growth of 

 interest in the system of Raunkiar in particular is a wholesome 

 sign that we are beginning to take a closer look at vegetation 

 and that we are gradually getting near enough to it to discern 

 the individual species of which it is composed. I do not mean 

 to commend the system of Raunkiar, which is too simple to fit 

 the d versities of the vegetable kingdom, even crudely as we 

 know them at present, and is based too largely on the single 

 feature of the location and size of the perrenating organs of 

 plants. Neither do I mean to commend the ''biological spectra" 

 of Raunkiar, which are of floristic interest but are rarely con- 

 structed from such data as to give them vegetistic value. 



