CHAP. II. CUTICLE. 41 



croscopes ; and, 3. None of those arts which the microscopic 

 observer knows so well how to employ, such as shifting, aug- 

 menting, or decreasing the light, interposing moveable sha- 

 dows between the mirror and the object, and the like, give 

 the least indication of the presence of any membrane across 

 the orifice of the stomate. I therefore conclude, that, in 

 Crinum amabile, the stomates are foi'med by two elastic kid- 

 ney-shaped bladders, lying over an opening in the middle of 

 a contracted area of cuticle ; that these bladders, when ex- 

 panded, meet, and press powerfully against each other, like 

 two opposing springs ; thus causing the elevated ridge-like 

 appearance visible in the axis of the stomate in the figure above 

 referred to ; and that, when contracted, they curve in an 

 opposite direction, separating from each other, and ceasing 

 to close up the aperture over which they lie. If it were pos- 

 sible to be absolutely certain of the accuracy of this description, 

 the structure of the stomate in Crinum amabile might be safely 

 taken as the type of all others ; for, no doubt, they are all 

 constructed upon a similar plan. Without actually asserting 

 so much as this, it may be stated, that, of many hundreds of 

 observations I have made upon this subject, I have not met 

 with any thing that has led me to doubt the uniformity of 

 their nature, or their general accordance with what is found 

 in Crinum amabile, whatever that may be. Or at least, the 

 only difference is this, that while the two bladders that form 

 the edges of the aperture are distinctly separated at their ex- 

 tremities in this plant, they are often confluent in others, as 

 in Caladium esculentum. (Plate III. fig. 9.) All this appears 

 fully confirmed by the curious observations of Mirbel, who 

 found that in Marcliantia the stomates are formed in the fol- 

 lowing manner. The appearance on the upper surface of this 

 plant of a depression with four or five bladders arranged in a 

 circle, is a certain sign of the commencement of stomates. 

 The bottom of this depression at a certain time is pierced by 

 a large square hole, either by the destruction of a central 

 bladder, or by the separation of the sides of four or five blad- 

 ders at their angles nearest the centre of the depression. 



Several varieties are represented at Plate III.,- besides 

 which, stomates have been noticed by Link to be occasionally 



