76 PBINCIPLES OF PLANT CULTURE 



121. Leaf development. — The cultivator should pro- 

 vide for normal leaf development. Since the protoplasm 

 of the plant is nourished by prepared food (58), and since 

 food preparation in most plants takes place almost wholly 

 in the leaves (120), it is of first importance that the plant 

 be so cared for as to promote normal leaf development. 

 Without this, good crops are impossible. The plants 

 must be grown far enough apart so as not to unduly shade 

 each other; insects and fungi must not be permitted to 

 prey upon them when it is possible to prevent it ; and the 

 leaves must not be needlessly removed or injured. The 

 more severe the climate, the more important is perfect 

 foliage, because more reserve food is required to endure 

 a long, severe winter than a short, mild one. 



122. Distance apart to grow plants. — When the 

 finest developed plants, or parts of plants, as fruits, 

 flowers, leaves, stems or roots, are desired, the plants 

 should not be grown so near together as to interfere with 

 each other's leaf or root development. But when the 

 largest crop from a given area is of more importance than 

 the development of the individual plant, as with grain 

 crops, the loss from a limited amount of shade and crowd- 

 ing will be more than made up by the increased number 

 of plants. In this case, the amount of crowding that will 

 give the maximum yield will depend much upon the 

 fertility and moisture of the soil, and must generally be 

 determined by experiment. 



123. Niunber of leaves — Stem and root development 

 depends on the number of leaves. Since the vascular 

 bundles, through the formation of which the stem and 

 root increase in diameter, originate in the leaves (67), 

 the size and firmness of the stem and the root depend 

 somewhat upon the number of leaves the plant bears. 



