184 HISTORY OF BOTANY 



after the recognition of the fundamental importance of 

 protoplasm. Seeing that this " physical basis of life " 

 was common to animal and plant it became necessary to 

 compare closely the methods of nutrition in the two 

 kingdoms and to follow out their differences and agree- 

 ments. Slowly the conclusion was arrived at that the 

 plant, as it were, started its nutritive processes at a 

 lower level than the animal, for it appeared not only to 

 carry out the various nutritive phenomena exhibited by 

 the animal in digesting and assimilating " food/' but 

 actually manufactured for itself the very " food " so 

 digested and assimilated, out of raw materials obtained 

 from the soil and the air. The term " food " thus came 

 to have a different meaning according as it was used in 

 connection with one type of organism or with the other, 

 and the want of appreciation of this fact introduced 

 much confusion in the numerous students' textbooks 

 that now began to make their appearance. 



Further, it was gradually recognised that plant proto- 

 plasm, like animal protoplasm, was sensitive and responded 

 to stimuli in various ways, some identical with those 

 exhibited by the animal, more often in ways totally 

 different, and that the nature of these responses was 

 determined chiefly by two factors, the one the special 

 capacity possessed by the plant of manufacturing " food " 

 from inorganic materials, the other its fixed habit and 

 diffused skeleton. 



The number of papers published between 1860 and 

 1900 concerned with the physiology of plant nutrition 

 was enormous. On the problem of photosynthesis and 

 the composition and functions of chlorophyll alone 

 more than seven hundred researches were published during 

 these forty years ; so that one is safe in estimating the 

 output for the whole of plant physiology at several 

 thousands. Very many of these were, of course, mere 

 notes, criticisms, or summaries, but, even if we halve the 

 total body of published work, the amount that must be 



