Plants in their Relation to Disease. 171 



vesea) with that of a cultivated variety (Wilder), the following marked dif- 

 ferences were noted : 



Wild. Cultivated. 



Potas.sinm oxide ' 22.06 49.24 



Sodium oxide 29.79 3.23 



Calcium oxide 14.88 13.47 



Magnesium oxide Traces. 8.12 



Fenic oxide 6.07 1.74 



Phosphoric acid 14.47 18.50 



Sulphuric acid 12.62 5.66 



99.89 99.96 



These relations are most striking, but not more so than those changes ac- 

 tually accomplished in the wild grape ( Vitift lahrusca). A comparison of the 

 ash of the fruit from a wild vine, with that of the fruit froin a vine transfer- 

 red from the same locality to the vineyard, where it was subjected to a care- 

 ful course of treatment, gives the following : 



Wild. Cultivated. 



Potassium oxide : 50.93 62.65 



Sodium oxide 0.15 0.85 



Calcium oxide 22.23 14.24 



Magnesium oxide 5.59 3.92 



Fenic oxide 0.79 0.53 



Phosphoric acid 17.40 13.18 



Insoluble matter 2.92 4.63 



100.01 100.00 



These changes, chiefly in the lime, potash and phosphoric acid, were di- 

 rectly correlated to variations in the amount of sugar and to the develop- 

 ment of other desirable qualities. They are most suggestive, and furnish 

 ample food for deep reflection. 



The influence of nitrogenous foods in stimulating growth is well known, 

 and according to the principles already laid down, this stimulation con- 

 stantly tends to the reduction of vital energy and the introduction of disease. 

 Under such circumstances, influences which otherwise might long have lain 

 dormant, now become active, and it is under such conditions that parasitic 

 growths often secure their firmest hold to destroy. The judicious applica- 

 tion of nitrogenous constituents in the food supply is a necessity of continu- 

 ous growth; but these elements of food should bear a definite relation to 

 those other constituents of food which tend to more perfect maturity of 

 structure ; or, as Lawes and Gilbert express it,* "A relative excess of nitro- 

 genous supply favors the extended growth of the organs of vegetation, pro- 

 longing their development, it may be, until the resources of the plant are 



* Mixed Herbage of Perm. Meadow, Phil. Trans. E. Soc. 1882, p. 1221. 



