WA TER-STOMA TA . 



ug 



and further growth- Our figures show several cases of such accessory cells of 

 the stomata. As a peculiarity of the guard-cells, it is moreover to be added, that 



FIG. 120.— Development of stomata on the leaf of Sedunt purpurascetts. j-t very 

 young; B nearly mature; e,e epidermis cells. The numbers denote the order of 

 succession of the divisions, 



they always contain chlorophyll-grains in somewhat large quantity, even when the 

 rest of the epidermis is devoid of them. 



There is no doubt that the stomata are originally destined for the exchange 

 of gases of the assimilating organs, and for the regulated discharge of aqueous 



Fig. I2t r)evelopment of stomata of /'^tf#'«^a*f//ate (a Fern). ..^ very young ; 



S almost mature ; e cells of the epidermis ; V preparatory divisions ; j- (in ^) mother 

 cell, which forms the two guard-cells {ss) in J, 



vapour. Nevertheless, these organs, as occurs so often elsewhere, may also ber 

 ftiade serviceable for totally different purposes; and thus we find in many cases, 

 especially in the highly organised Phanerogams, that stomata, but little modified 

 in other respects, are employed for the purpose of conducting to the surface water 

 excreted from the internal tissues. Such stomata, which are generaEy situated on 

 the margins of the foliage leaves or on the teeth of the leaf- margin, or more 



