Ch. Ill, 4] 



AXATOMY OF LEAVES 



29 



When the microscope is turned cUrectly upon a leaf, it 

 shows little, because the tissues as a whole are opaque. But 

 if from a t\-pical leaf a very thin slice or section be cut across 

 from surface to surface, it will show under the microscope 

 the general aspect presented in our picture (Fig. 8). Promi- 



FiG. 8. — A cross section through a tj'pical leaf, that of the European 

 Beech ; greatly magnified. The shaded round and oval grains are green in 

 the living leaf. (Drawn, with slight changes, from a wall chart by L. Kny.) 



nent in the view are the three tissues of the leaf, — the abun- 

 dant cMorenchyma, distinguished by the presence of chlo- 

 rophyll (in the shaded discoid grains of our picture) : the 

 veins, compact and without color (of which a large one 

 shows, on the left) : and the transparent epidermis, which 

 covers both surfaces. Also amongst the chlorenchjina 

 can be seen the various irregular and interconnecting air- 

 passages. The cells composing these tissues are incli\-idually 



