THE LEAF 



77 



it sometimes projects, or lies about level with the general surface. 

 But in plants of dry climates it is apt to be sunk inwards. This 



Fig. 52. 



Stoma of Aloe depressed below the well-developed epidermis. The thick cuticle 



is shown black. ( x 300.) F. O, B. 



is seen in slight degree in Narcissus (Fig. 51), but more distinctly 

 in Aloe (Fig. 52), a succulent plant with strongly cuticularised 



Fig. 53. 



Part of a transverse section of the xerophytic leaf of Hakea, showing a stoma 

 greatly depressed below the well-developed, and cuticularised epidermis, which is 

 propped out by thick-walled sclerotic cells. ( x 150.) F. O. B. 



epidermis. The stomata themselves are of the same type as Narcissus, 

 but seated at the bottom of deep pits. A more extreme case is seen 



