218 



lanceolate and directed obliquely or vertically upwards. Its 

 structure is isolateral (fig. 49). The epidermis is thick and 

 most of its cells on both surfaces have a thick mucilaginous 

 inner wall which in transverse section presents a characteristic 

 appearance, two light stripes showing between the green tissue 

 and the cell cavities of the epidermis. These cavities are 

 filled with tannic acid and the contents are therefore dark. 



Fig. 49. Stellera Lessertii. A, Leaf in transverse section. 

 B, a hair. X 203. 



There are stomata on both surfaces. The palisade cells occur 

 in 2 or 3 layers above and below; the centre is occupied by 

 the veins which take up most of the space; between them 

 there are 2 or 3 layers of rounded cells less rich in chloro- 

 phyll, and many "Speichertracheiden" (shaded in fig. 49). 



A young stem shows a thick but non-mucilaginous epid- 

 ermis with stomata which are not sunk; below this are 3 

 layers of rounded green- cells of which the outer ones are 

 slightly palisade-like. These are followed by about two layers 

 of round or tangentially extended cells containing a small 



