

HOLLY LEAF 133 



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 sur- 

 rounded 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 (1) 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. 



I. 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. 



The stomata are small in this leaf, as in most of the Dicotyledons, 

 and it is consequently somewhat difficult to make out the details 

 of their structure : for examples of larger and more easily observed 

 stomata, and the observation of the details of their structure, 

 reference should be made to the work dealing with the Mono- 

 cotyledons (p. 175, &c.), in which the stomata are often of con- 

 siderable size. 



V. Cut tangential sections from the upper and under 

 surfaces of the leaf of the Holly, and mount them sepa- 

 rately 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, 



