172 American Horticultural Society. 



exhausted or the season past. On the other hand, a relative excess of mineral 

 manures may bring on premature ripening. It is the proper adaptation of 

 the two descriptions of supply to the current requirements of the plant and 

 of the season, that gives both full, properly-proportioned and well-matured 

 growth." Nature, unmolested, preserves this relation ; but it is seriously 

 disturbed by that system of reckless cropping which man adopts in defiance 

 of both nature and sound business principles. Active diseases arising from 

 the causes thus indicated are only too familiar, as is well known in that dis- 

 order now causing such havoc in our peach orchards all over the country. 

 Nor does the influence of the soil cease here, since varying conditions of 

 moisture to an unusual degree, as well as the composition and mechanical 

 condition, must have their well-defined efiect, though it may not be to origin- 

 ate a disorder, but simply to hasten and augment the action of other causes. 



Meteorological conditions exert an important and often determining influ- 

 ence in the development of disease. Combined warmth and moisture in 

 excess are promotive of great stimulation, thus making it readily succumb 

 to acute disease, and this fact, in connection with the well-known influence 

 of such conditions in the promotion of fungoid parasites, enables us to see 

 that their effect is of a twofold and somewhat far reaching character, though 

 we may generally regard their action as indirect rather than direct. The?e 

 conditions are beyond our control, but modern methods and appliances do- 

 render it possible for us to lessen their destructive influence in a very ap- 

 preciable degree. Irrigation will counteract the effects of drought, but we 

 may even go beyond this, and by the judicious application of manures, 

 " adapting them to the requirements of the plant and of the season," as Lawes 

 says, do much towards checking the undue stimulation of warm, moist 

 Aveather. 



Injuries constitute a most prolific source of functional disorder. They are 

 of such a diversified nature that no general law is applicable to their treat- 

 ment; it rather becomes necessary to deal, first of all, with the special agent 

 by which the injury is produced, and afterwards with the injury itself. Dis- 

 orders of this character arising through the agency of insects are not only 

 oftentimes of a very grave nature, but they are sometime ; difficult to deal 

 with on account of the rapidity with which they may be distributed, thus 

 becoming far-reaching in their action. In many cases a proper knowledge 

 of the habits of the insect and its mode of development enables us to deal 

 successfully with them. Their action as direct pathogenic agents, as in the 

 production of galls and the destruction of foliage when feeding, is, perhaps, 

 most readily controlled. It is indirectly through ovipositing and the subse- 

 quent action of the larvae that insects often exert their greatest influence and 

 become most difficult to control. As in the common borers, their action is 

 usually very extended, and by operating upon the most highly vitalized tis- 

 sues of the plant, serves not only to directly reduce the general system, btit 

 introduces conditions which rapidly promote decay, and thus is induced a 

 diseased state which otherwise might not have obtained. In the scolytid. 



