HOLLY LEAF 81 



4. The spongy parenchyma, the cells of which resemble 

 those of (3) in general characters ; but their shape is various, 

 and large intercellular spaces occur. Idioblasts with crystals 

 are scattered here and there. Embedded between (3) and (4) 

 are 



5. Vascular bundles of various size ; the direction in which 

 these run is not uniform, as is naturally the case, since the 

 venation is reticulate : the positions of xylem and phloem with 

 regard to the whole leaf are the same as in the Sunflower : the 

 bundles are surrounded by a continuous colourless sheath of 

 cells (the bundle-sheath or endodermis) without intercellular 

 spaces. At the lower limit of the section lies 



6. The lower epidermis, which resembles (i) in general 

 character ; but differs in having numerous stomata. Note the 

 appearance presented where the two guard-cells of a stoma 

 have been cut transversely, and observe carefully 



a. The form and position of the two guard-cells 



b. The cavity or intercellular space between them (the pore) : 

 this leads into 



c. The large, intercellular space (air-cavity) in the tissue 

 beneath the stoma. 



d. In the sections stained with chlor-zinc-iodine or with 

 fuchsin, note the continuity of the cuticle round the guard-cells, 

 into the pore of the stoma. 



V. Cut tangential sections from the upper and under surfaces 

 of the leaf of the Holly, and mount them separately in glycerine 

 with the external surface in both cases uppermost. 



The cells of the upper epidermis are tabular, with irregular 

 outline ; the surface has a granular appearance, explained by 

 the granular cuticularized layers observed in transverse sec- 

 tions ; the lateral walls are pitted, the contents colourless, and 

 there are no stomata. 



The cells of the lower epidermis are similar to the above ; 

 but stomata are numerous ; they have no definite arrange- 

 ment. Note the two sausage-shaped nucleated guard-cells, 

 inclosing the pore ; they contain chlorophyll, and are slightly 

 depressed below the general surface. 



N.B. The Cherry Laurel (Primus Lauro-Cerasus) may be. 



G 



