174 BOARD OF AGRICULTURE. 



most part, presented in journals or other publications which are 

 quite out of the reach of the general student. These results, 

 together with the remarkable studies of English experimenters, 

 comprise nearly all which is positively known with reference to 

 the life and growth of agricultural plants. This widely scattered 

 mass of facts embraces, however, just what every progressive 

 farmer wants to know ; while not one in a million has the time, 

 the means and the ability to obtain, translate, digest and arrange 

 them for himself. It is in the highest degree creditable that one 

 of our Professors should undertake and satisfactorily accomplish 

 the formidable task of bringing order out of such a chaos. 



In the above named volumes Prof. Johnson has presented in a 

 convenient form, the established facts of Physiological Botany, so 

 far as they relate to the cultivation of crops, and he has stated in 

 clear language the cardinal principles upon which successful agri- 

 culture must depend. The following is from the Preface to How 

 Crops Grow : 



" For the last twelve years it has been the duty of the writer to 

 pronounce a course of lectures annually upon Agricultural Chem- 

 istry and Physiology to a class in the Scientific School of Yale 

 College. This volume is a result of studies undertaken in prepar- 

 ing these lectures. It is intended to be one of a series that shall 

 cover the whole subject of the applications of Chemical and Physi- 

 ological Science to Agriculture, and is offered to the public in the 

 hope that it will supply a deficiency that has long existed in Eng- 

 lish literature. 



" The progress of these branches of science during recent years 

 has been very great. Thanks to the activity of numerous English, 

 French, and especially German investigators, Agricultural Chem- 

 istry has ceased to be the monopoly of speculative minds, and is 

 well based on a foundation of hard work in the study of facts and 

 first principles. Vegetable Physiology has likewise made remark- 

 able advances, has disencumbered itself of many useless accumu- 

 lations, and has achieved much that is of direct bearing on the art 

 of cultivation. 



" The author has endeavored in this work to lay out a ground- 

 work of facts sufficiently complete to reflect a true and well-pro- 

 portioned image of the nature and needs of the plant, and to serve 

 the student of agriculture for thoroughly preparing himself to 

 comprehend the whole subject of vegetable nutrition, and to esti- 

 mate accurately how and to what extent the crop depends upon 

 the atmosphere on the one hand, and the soil on the other, for the 

 elements of its growth. 



" It has been sought to present the subject inductively, to collate 

 and compare, as far as possible, all the facts, and so to describe 

 and discuss the methods of investigation that the conclusions 

 given shall not rest on any individual authority, but that the stu- 



