No. 7. DEPARTMENT OP AGRICULTURE. 631 



is to find the causes and conditions necessary in each particular case. 

 He weighs the amount of water given olf under certain conditions, 

 he determines the method by which the various mineral constituents 

 are absorbed, he follows the path of these from root through stem 

 and leaves. He pursues the various changes which substances un- 

 dergo as they travel from cell to cell. He finds e. g. that starch is 

 first formed in the green part of the leaf with the aid of sunlight 

 and that this may be changed into sugar as it travels to another 

 part of the plant. He finds that the starch may again be formed 

 and placed in an underground storehouse for the following year. 

 Thus he knows that the starch which is present in enormous quan- 

 Tities in the potato was first manufactured in the leaves, changed 

 into sugar-like substances for transportation, and reconverted into 

 starch in the underground tuber. 



The scientist determines the conditions most favorable for the 

 activity of the leaf -green. He analyzes the sunlight and finds by 

 experiment which parts of this, the red, blue, violet, or yellow rays, 

 are most conducive to the proper exercise of this function. He 

 investigates the process of breathing by which the plant accumulates 

 the energy which it needs for its important work. Finally he 

 represents all the results he obtains by zizzag lines and curious 

 curves, much to his own edification, but to the distress of the un- 

 initiated. 



It has been found that the blackberry begins its starch-making 

 activity at 36 degrees F., this is called the minimum or least 

 temperature for this process in the case of this plant; this activity 

 ceases at 115 degrees F., which is therefore the maximum or 

 highest temperature; and at 77 degrees F., the starch making 

 activity is strained to the utmost. This then is for this particular 

 function, the optimum or best temperature, while of scientific im- 

 portance such exact data are of no practical interest. The gardener 

 approaches the optimum conditions of light, heat and moisture in 

 the greenhouse where he regulates temperature, transpiration and 

 light. Much of his knowledge comes from haphazard experiment, 

 as does indeed most of the valuable horticultural knowledge of the 

 present day. But all the world's great industries have had similar 

 beginnings, and men have found that systematic progress is only 

 possible if there is a scientific basis. Thus the manufacture of 

 dyes, glass, pottery, soaps, pigments, was practiced from times im 

 memorial, but what is all the knowledge of the ancients compared 

 to the progress made in chemical manufacture in a single year of 

 our present era? 



The i)hase of horticulture which is established on a purely scien- 

 tific basis is the study of soil constituents. It seems incredible that 

 our grandfathers knew nothing about this important matter. In 

 fact, the chances are, if they troubled themselves to think about it, 

 that they believed the plant to be endowed with a peculiar living or 

 vital force by means of which it might create the various plant pro 

 ducts out of nothing at all. In the 17th century another gold-maker, 

 Van Helmont, had proved to his satisfaction and to the satisfac 

 tion of succeeding generations that all that a willow required was 

 water. He proved this by experiment. He planted a willow which 

 weighed 5 lbs. jn a ve!=?sel wjth dried earth which weighed 200 lbs. 



