iv ENVIRONMENT AND LEAF-FORMS 209 



In a more recent paper Costantin has investigated 

 the same subject, and given special attention to the 

 influence of environment on the production of 

 stomata. 1 In Hippuris vulgaris the leaves which live 

 in water are long, thin, and sinuous, while in the air 

 they are short and thick ; in the water the epidermis 

 consists of short regular cells, bearing a number of 

 stomata, while in the water the cells are long, thin, 

 narrow, and bear no stomata. The writer has from 

 the same rhizome of Polygonum amphibium grown 

 two plants, one in water, the other in air, and while 

 the latter was provided with numerous stomata, the 

 former had none at all. This illustrates well the in- 

 fluence of environment on the production of stomata, 

 and in Stratiotes aloides stomata are seen to appear 

 on the leaves as they gradually emerge above the 

 surface of the water. But the most minute and 

 valuable investigations in reference to this matter 

 have been conducted by M. Pierre Lesage, and were 

 described last year 2 in his inaugural thesis. His re- 

 searches bear upon the question of the influence of 



1 Costantin, Influence du Milieu Aquatique sur les Stomatcs. Bull. 

 Soc. Botanique, 1885, p. 259. 



2 Pierre Lesage, Influence du Bord de la Mer sur la Structure dcs 

 Feuilles. Rennes, Oberthur, 1890. See also his Contributions a la 

 Biologic des Plantes du Littoral et des Halophytes ; Influence de laSalure 

 sur f Anatomie des Vegetaux, ibid. 1891, which contains an abstract of 

 many experiments performed after the publication of this thesis. 



