STRUCTURE.] STOMATES ARE SECRETING ORGANS. 149 



mouthed funnel, as a tube, and then constitutes what has 

 been described and figured by Gasparrini under the name of 

 a cistome. In this case the tube-like continuation of the 

 cuticle terminates in an orifice at the bottom of the epidermis ; 

 sometimes, however, appearing to continue for a short 

 distance into the portion of the air-hole lying between the 

 green parenchymatous cells; as in Cereus peruvianus and 

 Protea mellifera, which, however, has a simple epidermis. 

 That part of the cuticle which penetrates into the interior of 

 the leaf, is acted upon by iodine and sulphuric acid, as Payen 

 states, precisely as the cuticle situated on the outside of the 

 epidermis. 



With respect to a fibrous structure ascribed to this appa- 

 ratus by Gasparrini, Mohl observes that it can no more be 

 demonstrated in it than in any other vegetable membrane ; 

 but as bands resembling fibres occur on the cuticle of many 

 plants, so does the same appearance present itself in the 

 cistomes of some plants, as, for instance, of Cereus peruvianus 

 and Helleborus niger, &c. In like manner, as the cuticle 

 seldom admits of our distinguishing any trace of its being 

 made up of pieces corresponding to the subjacent epider- 

 moidal cells, so is it with its processes lying in the interior of 

 the leaf. They sink, indeed, into the furrows between 

 contiguous cells, and are frequently provided at those places 

 with projecting bands immersed in the furrows; but no 

 composition of originally distinct pieces can be detected by 

 the application of acids. (See Annals of Natural History, 

 vol. xv. p. 217 for further details, and the Elements of Botany, 

 p. 21, for figures.) 



Some physiologists, Link for instance, adhere to the 

 opinion that stomates are secreting organs, and not mere 

 passages in the epidermis for the transmission of gaseous 

 matter. Upon this subject I quote the words of Schleiden : 



" These two cells (of the stoma) have been designated by 

 the name of glands, but I do not see any reason for this 

 denomination being given to them in preference to any of 

 the other exactly similar cells of parenchym. From these 

 they do not differ at all in the abstract, and in their position 

 only apparently, inasmuch as it is a law that only two cells 



