Bbtts. — Autecology of Plants of I'eridofife Belt, Nelson. 281 



Figs. 5 and 6 show schematically a section through the upper part 

 and the middle of the lamina respectively. From these diagrams it will 

 be seen that small vascular bundles go to the ventral grooves and end 

 ju^t under the cells lining them. It is reasonable to suppose that these 

 cells are for the purpose of absorbing water and not exuding it. 



Fig. 7 gives the structure of the leaf in more detail. 



Both the upper and the lower epidermis consist of large, regular cells, 

 those of the upper surface being larger than those of the lower. These 

 cells have their external walls slightly thickened, and there is a thin 

 cuticle. Stoma ta are found on both surfaces ; the guard-cells are small, 

 have thickened walls, and are level with the surface. There are small 

 guard-cell ridges. 



Fig. 3. — Euphrasia Monroi. Uppor surface of leaf ( x 4). a, groove. 

 Fig. 4. — Euphra~sia Monroi. Lower surface of leaf ( X 4). a, groove. 

 Figs. 5, 6. — Euphrasia Monroi. Transverse sections through leaf (x 30). 

 a, vascular bundles ; h, cells in grooves. 



The chlorenchyma is differentiated, but only to a small extent. Practi- 

 cally the whole width of the leaf is occupied by spongy tissue ; the cells 

 just above the lower epidermis are more like spongy tissue, but the 

 transition between the two types of tissue is not very marked. The 3 

 layers of cells just below the upper epidermis consist of smaller cells which 

 are more or less rounded and have their walls slightly thicker than do 

 the rest of the mesophyll cells. The next 5 or 6 layers of cells are very 

 large, long cells. Just above the lower epidermis the cells are more irregular. 

 All the mesophyll cells contain numerous oval chloroplasts. 



In the furrows there are numerous projections for water-absorption. 

 These are formed of 2 cells which have their walls slightly thickened. 



