STATE AGRICULTURAL SOCIETY. 127 



becomes so practically, in most soils and climates, as a means of 

 enlarging, directing and economizing the use of the preceding 

 elementary bodies and influences. In the most favorable localities 

 of soil and climate, it greatly enhances the results of vegetable 

 growth, wliile, in unfavorable spots, it is essential to the security 

 of any useful result. In conclusion, the active coexistence of 

 these conditions are essential to all vegetable life, action and 

 result. They make the plant whatever it becomes. With the 

 exception of occasional impediments to health, (which need not 

 be mentioned in this hasty sketch,) they are the only considerations 

 to he had in mijid in the investigation of vegetable disease. Disease^ 

 from the very necessity of the case^ must be found in some dfficiency^ 

 intensity^ or irregularity^ in some one^ more or all, of these con- 

 ditions. 



2. Specific climatic requirements. — Light., Heat and Moisture.^ 

 in their relation to soil and air^ exert a combined iniluence which 

 is denominated, in its temporary aspect, season^ but in its usually 

 fixed condition, climate. Climate and season may be viewed in 

 three aspects. 



a. Intensity. — 1. Tropical plants, as a whole, require variously, 

 high heat and moderate degrees of moisture. Hence, they are 

 cultivated in what are usually denominated temperate climates, 

 only where those climates exhibit, during the summer, a degree 

 of heat and light closely approximating to that of tropical regions. 



The United States of America exhibit, through nearly all their 

 extent, such a character. Hence, in most of the central and north- 

 ern States, Indian corn, melons, cucumbers, tomatoes, &:c., grow 

 with a good degree of freedom, while, in the southern States, 

 sugar-cane, cotton, rice, &;c., are cultivated with facility and 

 profit. The United States of America, viewed in comparison 

 witli otiier temperate climates, resemble a gore extended into 

 them from the tropics, during one-third of the year. 



2. Hardy ]»lants, on the other hand, indispensibly re<|uire, at 

 least for a ]jart of the year, a degree of coolness and moi>ture 

 inconsistent with the healtli of tro])ical vegetation. These ele- 

 ments are afforded to them in the early spring and late autumn, 

 at periods when tropical })laiits are not in progress. This result 

 is farther reached by uniforiuly locating tropical jdants in the 

 warmest aspects, and liardy ones in those which are cooler. In 



