INFLUENCE OF WATER ON LAND-PLANTS 43 



3. The Heath or Ericoid Type (Fig. 12), characteristic 

 of many heath- plants e.g., Erica, Empetrum, Calluna. 

 The leaves are small and their edges are rolled under and 

 nearly touch, forming a chamber the entrance to which 

 is almost closed by hairs (see Fig. 9). 



4. In the Myrtle-Type the leaves are thick, leathery, 

 and evergreen, sometimes large, as in the Rhododendron, 

 sometimes small, as in the box. 



FIG. 11. TRANSVERSE SECTION OF ROLLED 

 LEAF OF THE MARRAM - GRASS (Psamma 

 arenaria). (MAGNIFIED.) 



a, sclerenchyma ; b, chlorophyll- tissue ; c, vas- 

 cular bundle ; d, epidermis. 



FIG. 12. Erica 

 Tetralix, SHOWING 

 HEATH TYPE OF 

 LEAF. (SLIGHTLY 

 REDUCED.) 



5. The Reed or Juneoid Leaf is long, smooth, and 

 circular. The transpiring surface is small, and as the 

 leaves are erect, the effect of the sun's rays upon their 

 surface is much reduced. 



6. The reduction of the leaf-surface may be carried 

 so far that modifications are rendered necessary in other 

 parts of the plant. When the leaf-system is too small 

 to accomplish the necessary assimilation, this work has 

 to be carried on elsewhere, either by the leaf-stalks, which 

 flatten out and become green and leaf-like (the phyllodes 



