STRUCTURE.] THEIR STRUCTURE VARIETIES. 139 



This structure of the stomate in Crinum amabile may be 

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

 constructed upon a similar plan, though modified in different 

 species. That is to say, they are composed of a pair of cells 

 placed side by side, communicating freely with a hollow 

 chamber in the parenchyma of the leaf built up of cells, 

 arranged in various ways. (Fig. 14, c represents the appear- 

 ance of the stomate in Acrostichum alcicorne when cut 

 through perpendicularly ; figs, d and g show it in the seed- 

 coat of Canna, and fig. f is the appearance of the same 

 stomate seen from above ; all these are copied from Dr. 

 Schleiden's figures.) It is not. however, always two cells 

 which by lying side by side form the stomate ; occasionally 

 a greater number is present; as in Marchantia, where, 

 according to Mirbel, the stomates are minute funnels in the 

 epidermis, composed of four or five vesicles arranged circu- 

 larly in several tiers ; at the bottom of this funnel is a large 

 square aperture, communicating with a subjacent chamber, 

 and caused either by the destruction of a central vesicle, or 

 by the separation of the sides of four or five vesicles at the 

 angles next the centre of the funnel. 



Several varieties are represented at Plate III.; besides 

 which, stomates have been noticed by Link to be occasionally 

 quadrangular, as in Yucca gloriosa (Plate III. fig. 10.), and 

 Agave americana, and by Brown to be very rarely angular, 

 of which, however, no instance is cited by that botanist. 

 The former case is one in which the quadrangular figure is 

 caused by the cellules of the opening being straight, and 

 bounded by four other cells which appear to be inside the 

 areolations of the cuticle. I have never been so fortunate 

 as to discover the membrane which this great observer 

 describes as generally overlying the apertures; nor do I 

 know of any other botanist having confirmed that observa- 

 tion. It cannot be the cuticle already described, because it 

 has been found that that part never overlies the stomates. 

 (See page 134.) 



Among the most remarkable forms of stomates, is that of 

 Equisetum hiemale, thus described by Dr. Golding Bird, in 

 the Annals of Natural History, vol. 18. " The fourteen longi- 

 tudinal ridges on each joint of the stem are each furnished 



