3 21 
The Leaf of Colliquaya odorifera, Molin. 
of collenchyma, roughly triangular in section, which forms a more or 
less prominent ridge, overlying, and parallel to, the median nerve 
(Fig. 24). Stomata occur on both surfaces, but they are more 
numerous and strongly developed on the upper one. The guard- 
cells are strongly thickened and slightly sunken (Fig. 20). Subsidiary 
cells, which are parallel to the guard cells, are present, the most 
Fig. 19. Fig. 20. 
Fig. 19. Surface view of a stoma with subsidiary cells. 
Fig. 20. Palisade-layer midway between median nerve and margin. 
Fig. 21. Palisade-layer nearer the margin with secretory cells. 
Fig. 22. Transverse section of the marginal portion of a mature leaf, 
h., hypoderm. 
common arrangement being that shown in Fig. 19, where there are 
two subsidiary cells on one side of the pore and one on the other. 
Sometimes a pair of subsidiary cells occurs on each side. 
Vascular Tissue .—The nerves are much branched and the 
ultimate branches anastomose freely. The xylem of the main 
nerves is strongly developed and consists for the most part of large 
