STRUCTURE.] CISTOMES. 147 



a stomate is thus established, and the cell, originally simple, 

 is divided, and forms the two cells of the pore. The cells 

 surrounding the pore become larger in consequence of the 

 general development of the leaf, and the intermediate slit 

 grows at a still greater rate. The mucosogranular mass con- 

 tinually increases in the interior wall of these cells, and a 

 communication is formed between it and the other sides of 

 the cells by means of filamentous processes. Lastly, in the 

 perfectly formed stomate the mass in the cells next the pore is 

 equally distributed in their interior, where grains of chloro- 

 phyll are formed. The development just described proceeds 

 very regularly in each stomate, but the same point of the leaf 

 does not always afford stomates equally developed. Stomates 

 are frequently found in a more advanced state than others 

 which are close to them." 



A supposed additional process of the stomates has lately 

 been discovered beneath the epidermis, of which the follow- 

 ing account is given by Mohl : 



" Gasparrini states, that beneath the stomates of the stem 

 of certain Indian Thistles (Cactacese), in particular of Cereiis 

 peruvianus, and also of the stem of Euphorbia officmarum, 

 and of herbaceous leaves, there is situated a vesicular organ, 

 which he terms Cistome. Its walls are said to consist of 

 delicate fibres connected by a membrane, which fibres form a 

 sphincter at the upper end of the cistome, beneath the closed 

 aperture of the stomate. These cistomes Gasparrini separated 

 with the cuticle from the epidermis by boiling the latter in 

 dilute nitric acid. Hartig, in his Lehrbuch der Pflanzenkunde, 

 part. 4, 1842, describes the same organ as an appendage of 

 the cuticle. Pay en states that the cuticle enters the stomates, 

 and in Cereus peruvianus, extends down through the layers 

 of epidermis as a thin membrane having the form of a muff. 

 This membrane, like the cuticle, is said to be coloured yellow 

 by iodine, and to exhibit the same resistance to the action of 

 sulphuric acid." In verifying these statements Mohl soaked 

 sections of leaves in tincture of iodine, washed them with 

 water, and then submitted them to the action of sulphuric 

 acid. This latter agent not only heightens the yellow tintf of 

 the cuticle coloured by iodine, but it has the additional 



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