Betts. — Aufecolof/f/ of PJaiifs of Peridotite Belt, Xelsoti. 



139 



Anatomy. 



Leaf (fig. 2). — The upper and the lower epidermis consist of large more 

 or less squarish cells with thin walls. There is a thick cuticle on both 

 surfaces. Stomates are found on both faces of the leaf. The guard-cells 

 are level with the u})per surface of the epidermal walls, but are below the 

 cuticle. The guard-cells have thickened walls, and the stoma is protected 

 by the guard-cell ridges. 



The chlorenchyma is rather feebly differentiated. The palisade tissue 

 consists of 4-5 rows of oval cells with very slightly thickened cell-walls, 

 and containing a small number of large chloroplasts. The 2 outer layers of 

 palisadic tissue are compact, but the inner ones are not so closely arranged. 

 There is also palisade tissue on the lower surface of the leaf. Here it is 

 only 1-2 rows of cells. The spongy tissue consists of rather irregular 

 loosely arranged cells, so that there are large intercellular air-spaces. These 

 cells also contain large chloroplasts. 



a- 



Fig. 2. — Hymenanthera dentatu var. alpina. Transverse section of lamina 

 of leaf ( X 230). a, thick cuticle ; 6, palisade parenchyma ; 

 c, bundle-sheath ; d, xylem ; e, jihloem ; /, guard-cell i-idge. 



The vascular bundle is of the usual dicotyledonous type ; the amount of 

 lignified tissue in the xylem is small. Surrounding the bundle is a sheath 

 of large thin-walled cells, which are practically devoid of chloroplasts. 



Stem (fig. 3). — The cork forms a wide band, and consists of fairly large 

 cells with thickened walls. Then conies the phellogen of thin-walled 

 rectangular cells. 



The cortex forms a layer of tissue 12-14 cells deep ; its cells are oval and 

 have thickened walls. There are numerous intercellular air-spaces, most 

 of which are, however, small. Drops of oil are found in the cortical cells. 



The pericycle fibres form small isolated groups. The cells are small 

 and have very thick walls, so that the cell-cavities are almost obliterated. 



