230 Wisconsin State Horticultural Society. 



Now, what makes the sap rise? Is it heat? We see that heat 

 and moisture are necessary to promote the sprouting of the seed 

 and the early development of the plant, and whether these are the 

 causes of the upward flow of the sap or not, we see that the flow 

 is greater when heat and moisture are in excess. If the flow is 

 too great for proper circulation in the leaf, whether it comes from 

 injury to the leaf, as stated before, or from a natural insufficiency 

 of foliage to meet extra circulation, the sap stagnates in the leaf 

 cells, and decay or loss of vitality sets in, which in turn induces 

 rust, mildew, fungoid growth or blight. Here is the starting 

 point of the trouble; a diseased or insufficient foliage impairs the 

 vitality of fruit, leaf, stalk or tree, and favors parasitic growth. 



Some claim that blight is contagious. Eust, mildew and fun- 

 goid growth may be, where they have once gained a foothold, but 

 blight cannot be. It is generated in every pore, cell or globule of 

 the single leaf, or of all the leaves on the twig, or part affected, 

 at the same time, and thus gives the conditions necessary to the 

 development of fungoid growth or rust. 



'" But why are not all varieties of vegetation attacked with rust 

 alike? Why are not all the leaves and parts of the plant at- 

 tacked affected alike ? It must be evident to all who have ob- 

 served carefully, that this trouble begins with the tenderest parts, 

 with the leaves just starting out and yet 'undeveloped, and that 

 after they get to be mature, and the buds are perfected, the dan- 

 ger is over. It is only while the plants are growing and tender, 

 when they are developing rapidly and the flow of sap is greatest 

 and the heat up to and over ninety degrees, that they seem to be 

 seriously affected. This is the tender period, the crisis in their 

 development, and once past it, they are safe. Slow growing vari- 

 eties and varieties with thick leaves, also those trees and plants 

 that reach maturity early, are less affected than the others. This 

 would suggest as a preventive remedy the cultivation of these 

 varieties, and such culture as would tend to produce a steady, 

 slow growth and early maturity, and the checking of excessive 

 and rank growth. The necessity of the last point is proved by 

 the results often seen to follow the stimulation to rapid growth of 

 slow growing trees that have been healthy and fruitful for years, 



