BY A. G. HAMILTON. 153 



vestiture of hairs, those on the outside being a beantii'ul c^ohlen- 

 brown, and tlioso beneatli silvery. They are spindh'-sliapcd and 

 tliiek-walled (Fig. 2). They fall off soon after the leaf has readied 

 full size. 



The stomates are found on both sides. They are sunk beneatli 

 the surface, and open into a vestibule formed by an upward arr-li- 

 ing of the surrounding epidermal cells, the aperture being at one 

 end of the chamlier, and directed towards the apex of the leaf. 

 The chamber is OOG mm. long, 004 mm. wide, and the aperture 

 001 mm. in diameter. The stomata are numerous, as many as 120 

 to the square millimetre, making about 120,000 to an average- 

 sized leaf. The e]3idermal cells are small, 001 mm., and rounded 

 in form. 



Seen in transverse section, the epidermis is composed of small 

 cells, about 0005 mm. high. The cuticle is very thick, 0015 ram. 

 (Fig. 3), of a dull olive-brown colour after the rest of the leaf has 

 been decolorised by spirit. The cells are usually empty, but now 

 and then contain cubical crystals. Scattered about in the epidermis 

 are found capitate hairs in sunken cavities (Figs. 6-7). In the 

 young leaf, these hairs are more plentiful. The interior wall of 

 the epidermis projects downwards into the palisade tissue(Fig.6a). 

 The hairs are thick-walled, and apparently empty; but the cavity 

 stains with saffranin or gossypimin very deeply. 



In the young leaf, the hairs project above the surface of the 

 epidermis, and apparently as the leaf gets older, the cuticle grows 

 up, so as to surround the hairs. Many of the hairs drop off while 

 the leaf is young, and the portions of the epidermis, on which they 

 were seated, grow up to the level of the rest, leaving no trace of the 

 former existence of the hairs. 



The mesophyll consists of palisade cells in two layers under each 

 face of the leaf. The cells are rather large, 0-06 mm. long, and 

 00075 mm. wide, packed with rather large granular chloroplasts. 

 There are no intercellular spaces, except just under the stomata 

 (Fig. 5). Between the two layers of palisade cells, the meso]ihyll 

 consists of irregularly rounded cells, containing chlorophyll, and 

 measuring 004 to OOC mm. in diameter. There are no intercellular 



