168 American Horticultural Society. 



increased, chiefly, however, within the last few years, which seem to mark a 

 period of particular activity in the field of vegetable physiology. And thus 

 in this connection, sucli names as those of Loraner, Hartig, Frank, DeBay, 

 and others have become very familiar. The tendency hns been largely, 

 however, to regard the question of disease from the standpoint of origin in 

 visible cause, such as injuries of various kinds; the action of insects, and 

 particularly the development of parasitic forms ; overlooking to a large ex- 

 tent the more primary and possibly greater influence of nutrition. In this 

 latter direction, however, we have the valuable results of Nobbe, Schroeder, 

 Erdmann, and others, who, by their careful researches into the special nutri- 

 tion of the plant, have essentially demonstrated in a very decisive manner 

 what De Saussure inferred from his earlier experiments, viz.: that all the 

 mineral constituents usually present in the ash of plants are essential to the 

 normal growth and perfection of the organism ; and that while certain con- 

 stituents are relatively more important than others, complete exclusion of 

 any one from the food supply will sooner or later result in more or less con- 

 spicuous malformation of structure or deblity of function. These relations 

 were most strikingly illustrated in those now classical experiments with 

 buckwheat, in which chlorine and potash were separately and collectively 

 withheld. Depriving the plant of potash, it was seen that there was imper- 

 fect assimilation, as manifested both in the abnormal color of the leaves and 

 the absence of starch from those tissues where it should have been present. 

 Supplying potash but withholding chlorine, starch was found, but there was 

 failure in its distribution to the centers of active growth, hence it became 

 largely accumulated in the tissues where formed. As a necessary concom- 

 itant of this condition, the entire plant soon lost its normal color and became 

 sickly and yellow, while there was also strong atrophy of the newly-formed 

 organs. Restoration of the chlorine and potash in the form of muriate of 

 potash seemed to restore the plant and its disordered functions to their 

 normal condition. More recently, similar abnormal conditions have been 

 found to be developed in the peach when suffering from the yellows, and a 

 restoration has in this case been also fully effected by the use of muriate of 

 potash as a specific. Indeed, the results obtained from direct experiment 

 and analysis during the past fifteen years, as well as several hundred well 

 attested cases in which the practical application of the principles involved 

 to large orchards has given most decided and favorable results, show that, 

 so far as this disease is concerned, we have already passed beyond the exper- 

 imental stage, and may now reasonably expect to find those whose orchards 

 are suffering from this most destructive disorder, ready to treat them ac- 

 cording to rational methods. 



We thus see that these elements of food have their specific functions, and 

 so, doubtless, have the various other elements found in the ash of the plant. 

 One fact in this connection, however, must be kept closely in mind, and that 

 is, that particular elements, or compounds, do not necessarily perform iden- 

 tical functions in all plants. For the same species, certainly, and perhaps 



