CHAPTER IX. 



THE MESOPHYLL. 



Spongy mesophyll and palisade cells Transverse section of leaf 

 Mesophyll-cell Intercellular spaces and gas-interchanges 

 Stomata The intercellular labyrinth Phenomena to be met 

 with in the labyrinthine tunnels Day and night changes 

 Chlorophyll-corpuscles Protoplasm and other cell-contents 

 Eunctions of chlorophyll-corpuscles Starch Photo-synthesis, 

 or carbon-dioxide assimilation. 



The mesophyll forms a sort of spongy filling-up tissue 

 between the epidermis and the vascular system, as we 

 have seen, and the green colour of the leaf is entirely due 

 to the countless millions of minute brilliant green bodies 

 contained in the mesophyll-cells, and called chlorophyll- 

 corpuscles. 



The spongy soft feel of the mesophyll is due to the 

 fact that the cells are throughout the greater part of the 

 mesophyll not closely in contact on all sides, but have 

 relatively large or small intercellular spaces separating 

 them one from the other except at certain points where 

 they abut on their neighbours, or on the vascular bundles 

 of the venation, or on the epidermis. 



Were it not for these intervening spaces, which contain 

 only gases and vapour, the fresh leaf would be quite hard 

 and elastic to the feel, because each mesophyll-cell is a 



