74 LEAVES. 



(41) Mate, or Paraguay Tea. 



The leaves of Ilex paraguayensis (N.O. Ilicinese) . 



The upper epidermis is composed of small polygonal isodiametric 

 cells (15 to 30/u), covered with a very thick striated cuticle; it is 

 devoid of stomata and hairs. 



The lower epidermis is composed of cells resembling those of the 

 upper epidermis in shape, but of smaller size. It bears very 

 numerous stomata, as well as a few water pores. The former are 

 surrounded and partially overhung by a circle of four or five sur- 

 rounding cells ; the water pores are larger than the stomata. 

 There are also a few unicellular, thick-walled hairs on the lower 

 epidermis. 



Above the veins the cells of the epidermis are nearly rectangular 

 and very regularly arranged. 



The mesophyll is heterogeneous and asymmetrical ; some of the 

 palisade cells contain crystals of varying form and size. The 

 spongy parenchyma is composed of very irregular stellate cells. 



The midrib is bi-convex. Next to the epidermis of both upper 

 and lower surface is a layer of collenchymatous tissue. The cells 

 of the cortical parenchyma contain numerous prismatic and cluster 

 crystals of calcium oxalate. The wood is composed of a large, 

 lower crescent-shaped portion, above which are two smaller slightly 

 radiating upper portions ; the whole is surrounded by bast and by 

 lignified pericyclic fibres. 



The diagnostic characters of powdered mate* are : 



(a) The small epidermal cells. 



(b) The thick striated cuticle. 



(c) Occasional unicellular conical hairs. 



(d) The presence of pericyclic fibres. 



(e) The numerous crystals of calcium oxalate. 



(f) The stomata surrounded by a circle of cells. 



