BOTANY 171 



ing. This is a profitable bit of botanical history for those 

 persons who are always crying "Of what use is it?" when- 

 ever any seeker after truth tries to find the north pole of 

 any sphere of knowledge. 



But, as Sir Isaac Newton remarked of his own achieve- 

 ments, we have only touched the shores of the ocean of 

 botany, and gathered a few of the more readily obtained peb- 

 bles. The unsolved problems are more numerous, and at the 

 same time more difficult, more elusive, and more fascinatingly 

 attractive than those that are solved. The discoveries of 

 Mendel and de Vries raised far more questions than they 

 solved. What, for example, is the mechanism of heredity? 

 How is protoplasm built, and how does it behave in order 

 to produce the results of Mendelism and mutation? Here 

 we have theories and to spare. For the botanists, de Vries 

 has proposed the theory of intracellular pangenesis; for the 

 zoologists, Weismann has conceived the theory of the germ- 

 plasm. But time forbids even an enumeration of them all. 

 The significant and hopeful sign is that there is now no at- 

 tempt to squeeze and distort the facts to fit the theories. 

 The theories are used only to point the way to the next ex- 

 periment, for it is clearly recognized that only by observation 

 and experiment can we ever even approximate an explana- 

 tion of the mechanism of heredity. 



The method of organic evolution, the causes of sexual 

 differentiation, the origin of life itself are questions still un- 

 answered, but now being vigorously attacked. In recent lit- 

 erature the question of mechanism versus vitalism is again 

 assuming prominence. Is the plant or animal a machine 

 which can be explained in the terms of mechanics, or is there 

 a further factor, a vital force, that must be taken into ac- 

 count? I have no intention of discussing this question in 

 detail, but it will be instructive in this connection to refer to 

 a recent experiment of Paul Becquerel of Paris. A number 

 of seeds of alfalfa, wheat, and mustard were dried for six 



