132 PLANT WORLD. 



interested in the plants. These openings soon became known 

 by the name of "stomata" or as the less euphonious angli- 

 cised form has it, "stomates," since they impress one at first 

 sight as small mouths. That they are analogous to the 

 mouth in the animal is a notion to be commonly met with 

 in the elementary text-books, justified however, only on 

 slender grounds, and too often leading to a distorted con- 

 ception of the purpose of the stoma in the economy of the 

 plant. This is, however, not the only more or less inade- 

 quate or indeed misleading idea about this organ presented 

 in the text-books, as it will be the object of this account, in 

 part, to show. 



It has happened that the study of the stoma, historically 

 considered, has been prosecuted in two general directions, 

 in that of structure and mechanical operation, and in that of 

 physiology. This does not mean that botanists who have 

 studied one of these phases of the subject have always done 

 so to the exclusion of the other, but it would contribute no 

 important or essential detail to the discussion to go into the 

 details necessary to the exact presentation of the history of 

 the study. On the anatomical side, the stomata of a multi- 

 tude of plants have been studied merely as details necessary 

 to a full know^ledge of the structure of plants; they 

 have been studied comparatively with the hope of resolving 

 the manifold forms into phylogenetic types; these manifold 

 forms have been examined with the puipose of showing that 

 this type is more or that less effective with reference to a 

 particular mechanical operation, especially as controls of the 

 diffusion of water-vapor out of the plant commonly known as 

 transpiration; and, regarding them as mechanisms pure and 

 simple, their peculiar mode of operation, and the anatomical 

 details contributory to it, have been the subject of the most 

 masterly examination.. The amount of detailed knowledge 

 thus gained is very great, and a mere citation of the papers 



containing it would be quite imposing. Among these many, 

 the essay of Schwendener will always stand as the master- 



