THE STUDY OF LEAVES. 



221 



box, or laurel, place it in a slit made in a piece of pith and 

 cut thin sections by means of a sharp razor, keeping the 

 razor wet with alcohol. Place the sections on a glass slip 

 in water and examine, selecting the thinnest parts for 

 study. Similar sections may be obtained by rolling up a 

 large leaf, e.g. rhododendron, and cutting without pith. 



A study of such sections shows that the tissue of 

 the leaf is much more closely packed towards the upper 



GLAND-HAIR-. 



LOWER _ 



EPIDERMIS 



-- SHEATH 



WOOD-VESSELS 



BAST 



-SHEATH 



Fig. 89. Portion of a leaflet of Broad Bean, magnified so as to show the arrange- 

 ment of its parts. 



than the lower side. The arrangement is as shown in 

 Fig. 89. 



Immediately beneath the upper " skin " (epidermis) 

 there is a layer of cells which lie close together and which 

 are arranged with their long axis across the thickness of 

 the leaf (palisade cells), while beneath these the cells are 

 arranged loosely in columns so that there are numerous 

 interspaces (spongy tissue). By stripping off the lower 

 epidermis a small fragment is sufficient and examining 

 with the microscope a very large number of openings 

 (stomata) leading into these spaces will be seen. Similar 



