The Various Ways in Which Plants Appeal 7 



fullest only by those who fare the farthest, the pleasures of science 

 are by no means unknown even to youthful students; and I have 

 myself experienced in the past and have since noticed in others, 

 a keen enjoyment in the use of exact scientific methods and tools, 

 a great satisfaction in the acquisition of knowledge that one feels 

 to be solidly grounded, and a lasting pleasure in an understand- 

 ing of the workings of the greater natural phenomena. But while 

 the personal and aesthetic elements are certainly by no means 

 absent from scientific study, as indeed the accompanying picture 

 will bear witness, the student must realize that the deepest 

 pleasures of science are of stern and spartan sort, somewhat 

 like those felt by the strong man when he rejoiceth to run a 

 race. 



We must return for a moment to the matter of the unity of 

 botanical science in order to consider yet another concession, 

 besides its artificial divisions, to human limitations. This unity 

 of the science is of course but a reflection of the unity of Nature, 

 where all of the vast number of facts and phenomena intergrade 

 and interlock without any real boundaries. Yet the mind of 

 man is so made that it can grasp only definite conceptions, and 

 not many of these; and it can no more form a definite image of the 

 infinite intergradation of phenomena than it can of the infinite 

 largeness of space or the infinite smallness of the sub-constitution 

 of matter. Hence it is necessary, for purposes of education and 

 exposition, to create definite images out of indefinite material. 

 Take, as an example, the subject of leaves. Leaves are so many, 

 so diverse, so intergradient, that no learner can grasp any con- 

 siderable proportion of the facts about leaves as they actually 

 are. The substitute therefor, to which every teacher and author 

 is obliged to resort, is a subjective conception of a generalized 

 or average leaf, built up for the learner from observation of a 

 number of actual leaves; or, better, it is a composite conception 

 of a leaf built up in the receptive mind of the learner from many 

 observations of actual leaves, much as composite photographs 



