LEAVES, THEIR STRUCTURE AND EUXCTIOXS. 



19 



FiH". 10. 



As stored in tlie cells of tubers, 

 seeds, or rouud the buds in matured 

 wood. 



up stores of carbon, partly for the individual good of the plant itself, hut mainly for the 

 good of the race, i.e. of its own S3eds and offspring. Note that starch and all other plant 

 products are rcallj' made or formed in the green leaves, but 

 that they are transformable, and may be stored up or used 

 in or by any organ as part of the plant. 



Let us glance at the structure of the leaf, and see 

 how its work is done. As everyone should know, leaves 

 are generally flattened expansions of the stem, covered 

 on both sides with a skin or cuticle of water cells, this 

 skin being full of holes, or mouth-like pores, called stomata 

 [stoma =0. little mouth). There are hundreds or thou- 

 sands of these pores (Fig. 11) on every square inch of 

 ordinary leaves, as you may sec if you skin off a bit of 

 leaf, and put it under a good microscope. A criuum, or 

 lily leaf, shows them plainly, with a good platyscopic lens. 

 In hydrangea and syringa (lilac) there arc one hundred and fifty thousand or more of 



these pores or mouths to the square 

 inch. 



Leaves must be large or full-sized, 

 healthy, and clean, in order to do their 

 best work. They require all the sun- 

 shine available short of scorching, blister- 

 ing, and other physical injury, caused 

 by a lack of moisture at the roots, or 

 enfeebled groAvth in a too close and 

 vitiated atmosphere under glass. See- 

 ing that each leaf depends for its full 

 action on the thousands of stomata which 

 stud its cuticle, you will at once per- 

 ceive the need there exists for syringing, 

 sponging, and otherwise cleaning plants 

 that grow under glass, or in or near 

 dusty roads and smoky towns. j\[uch of the freshness and successful cultivation in the 

 town squares and public gardens in Paris and elsewhere on the Continent is due to 



Fig. 11. Stomata. 

 Opening and closing pores in the outer coverings of 

 leaves for purposes of absorption, exudation or evaporation. 



