PEOCEEDINGS OF THE OHIO ACADEMY OF SCIENCE. 317 



as yet explored but little. Two decades ago, botanists had 

 scarcely thought of irritability not attended by visible reaction, 

 and we do not yet know the relation between irritability and 

 changes in protoplasmic composition. Nor do we know how 

 impulses travel in plants, though a good deal of attention has 

 been devoted to the subject. 



Only recently has root physiology received much attention. 

 For a decade and a half, diligent work has been done respecting 

 soil physics and chemistry, and definite knowledge of root func- 

 tioning is required before the results can be utilized in agricul- 

 ture. With the theory of excretion of toxins or other poisonous 

 substances by roots, has arisen the idea that soil sterility is not 

 commonly due to lack of requisite nourishing substances, but 

 usually to the presence of ])oisonous substances which retard 

 growth, or to unfavorable physical soil corriposition. Root phys- 

 iology and ecology, the study of soils, and practice in the use of 

 fertilizers should go forward together. The part played by 

 roots, by soil bacteria, and by fertilizers, in the destruction of 

 poisonous toxins in soils, is a problem, the solution of which is 

 of immense importance. 



The physiology of rei:)roduction is an inviting field, possess- 

 ing many unsolved problems. Sexual fusions probably arose as 

 a nutritional process. With the evolution of sex, may have come 

 a change of function, by which fertilization in higher organisms 

 may act mainly as a stimulus. It would seem from certain 

 experiments that sex may be controlled, at least in certain or- 

 ganisms. Yet some physiologists insist that sex is determined 

 by internal, uncontrollable factors. Sexual purity is questionable, 

 even in gametes, and sexual reversion may be Ijut a reversion of 

 dominance and latency. Whether sexual reproduction aids or 

 hinders variation is not determined ; and we know exactly neither 

 what sex is nor wdiat are the advantages and the disadvantages 

 of sexual reproduction. 



Though our knowledge of physiology is meager, the outlook 

 is as encouraging as the result"^ to be obtained are important. 

 In place of former notions of vital force and fanciful teleologic 

 and anthropomorphic expressions and explanations, plant, phys- 



