SCAR OF LEAF 143 



Observe, under a low power, the deep and narrow pocket lined 

 with an epithelial layer, ^diich gets deeper towards the base, 

 while vascular bundles form an irregular plexus below the base 

 of the pocket. 



Starting from the outer lip of the gland, examine the super- 

 ficial lining under a high power, and observe that there the 

 epidermis is a simple layer of cells of no great depth, and with a 

 thickened outer wall : passing down the inner surface of the 

 pocket, the cells become gradually deeper and narrower, and 

 occasional periclinal divisions may be seen, till at the base the 

 glandular epithelium may consist of three irregular layers of 

 cells, with thin cell- walls, dense protoplasmic contents and 

 nucleus. 



Treat another section with a drop of sulphuric acid : the super- 

 ficial cuticle resists the acid. 



The subjacent tissue may be examined for ends .of the latici- 

 ferous tubes, in which a number of nuclei may be found in the 

 stained sections. 



Sections should also be cut through nectaries of various 

 flowers : species of Fritillaria will be found to be good material 

 for this work. 



Leaf -scars and Fall of the Leaf. 



On twigs of the Elm cut in winter, note the buds, 

 both terminal and lateral, and below each an oval scar, 

 which indicates the surface of separation of a leaf when 

 it fell in autumn : the surface of the scar is brown, and 

 the slightly projecting dots upon it are the broken ends 

 of the vascular bundles which ran out from the stem 

 into the petiole. 



Cut longitudinal sections so as to pass through a scar, 

 and select for observation one of those which has 

 followed up the course of one of the vascular bundles to 



