THE LEAF 129 



a temperature of 1,300 degrees centigrade to break 

 down and build up that chemical change. Here in 

 this wonderful leaf cell factory it is going on all the 

 time, quietly and efficiently, making out of air and 

 water its own food and storing its surplus supply 

 away just as we do. 



The cells of leaves themselves are irregular in 

 shape and full of granular jelly-like substance called 

 protoplasm, which is considered the basis of all life 

 and is almost identical in both plant and animal 

 tissue. To give an idea of how many and various 

 shapes these cells are in a leaf and the action going 

 on, imagine a small narrow leaf i/g of an inch wide, 

 under a high power microscope. You would see per- 

 haps six or eight cells with a nucleus and twenty to 

 seventy chlorophyll grains in each and if you looked 

 carefully many other things. If you started looking 

 at the edge of the leaf and then by mechanical means 

 moved the leaf slowly the i/ s of an inch across the 

 lens of the microscopein that journey of \/% of an 

 inch you would see a thousand or more cells. At the 

 beginning of the journey, on the edge of the leaf, 

 the cells would be very narrow; going inland they 

 resemble somewhat cells in a honeycomb, irregular 

 in shape and outline. In each one is a continual pro- 

 cession of the chlorophyll grains going around and 

 around endlessly. Continuing on you would pass 



