176 MASSACHUSETTS HORTICULTURAL SOCIETY. 



information, namely, a knowledge of the special wants of the plant 

 under cultivation as regards the absolute amounts and relative 

 proportions of the various essential articles of plant food, and a 

 familiarity with the composition and the general physical proper- 

 ties of the different kinds of raanurial matter at our disposal. 



A brief statement of the principal results of a systematic and 

 careful examination into the circumstances which control a healthy 

 and vigorous growth of plants may show in what special directions 

 the growth of many of our garden and fruit bearing plants needs 

 more experimental investigation, to secure a more relial)le l)asis 

 for a proper mode of cultivation with reference to an eflicient sup- 

 ply of suitable plant food. 



First. All our cultivated plants on the farm, in the garden, and 

 in the orchard contain the same elementary constituents, yet no 

 two of them in the same absolute amounts and relative propor- 

 tions. The list comprises carbon, h3Hirogeu, oxygen, nitrogen, 

 sulphur, phosphorus, potassium, sodium, calcium, magnesium, 

 silicon, chlorine (manganese?). 



Second. These plant constituents are furnished in part by the 

 'surrounding atmosphere, in part by the soil, and some in varying 

 proportions by both. 



Third. The essential plant constituents are not needed in dif- 

 ferent plants in the same invariable proportions at the various 

 successive stages of growth, but are wanted at different stages of 

 growth in different absolute amounts and relative proportions. 

 P2ach plant has its especial wants at different stages of its devel- 

 oi)ment. Grain crops require much nitrogen in an available form 

 during their later period of growth, when blooming and forming 

 seeds ; grapevines need a large amount of potash during the 

 growing and maturing of the grapes. 



Fourth. The absolute amount of essential mineral constituents 

 may vary in the same plant without affecting, as a rule, the 

 general character of that plant ; yet not one of the essential ele- 

 mentary mineral constituents can serve in place of another one to 

 any marked extent without altering, in many instances in a seri- 

 ous way, the relative i)roportion of the organic constituents of 

 plants. Quite a number of our cultivated plants are more or less 

 susceptible of change in that direction, in consequence of a liberal 

 application of one or the other essential articles of plant food. 

 These changes are as apt to be in our favor as against our best 

 interests. 



