MICROSCOPIC OBJECTS. 11 



Fig. 21. Cuticle of an Orchis (Oncidium ?), x 120. 



This cuticle seems to have rather dark stomata, placed in 

 the centre of some of the cells. What appear to be holes, 

 are really papillae on the surface of the cuticle. In this case 

 the cuticle would no doubt absorb the moisture from the 

 atmosphere much more quickly than in the ordinary form of 

 cuticle, with its larger number of stomata and guard-cells. 



The cuticle seems to show best when mounted dry. 



Fig. 22. Cuticle of Chrysanthemum (Chrysanthemum 

 Sinense), x 300. 



Cuticles of plants, of which this may be taken as a type, form 

 a skin consisting of variously shaped cells with stomata, and 

 in some cases hairs scattered at intervals over the surface. 

 This cuticle was taken from the common garden Chrysanthe- 

 mum, and has hairs as well as stomata. Stomata have often 

 four guard-cells (see also fig. 24), but sometimes only two 

 (fig. 23) . Stomata occur chiefly on the undersides of leaves, 

 except in water-plants, in which they are found on the upper 

 surface of the floating leaves. They are sometimes found on 

 the collum of the apophyses of mosses, as in Funaria hygro- 

 metrica &c. The use of the stomata is to admit air to the 

 intercellular spaces of leaves &c. ; and no doubt they are 

 placed on the under surfaces to prevent their being choked 

 up with dust and other foreign matter. 



This object may be mounted in liquid. 



c 2 



