PROCEEDINGS OF THE OHIO ACADEMY OF SCIENCE. 315 



sues are less fixed than was formerly supposed and are of little 

 value, compared with the less plastic reproductive and vascular 

 tracts, as a basis for phylogenetic considerations. Experimental 

 morphologists have recently given attention, also, to the effect 

 of removal of parts, in changes induced in the form and the 

 functioning of other parts, have been able to inhibit development 

 of organs, both vegetative and reproductive, to inhibit or to 

 induce various kinds of reproduction, and have given us the 

 mutation theory with its observation of the origin of new forms 

 called elementary species. The day seems to be at hand when 

 we may accomplish results of great scientific and economic im- 

 ])ortance through control of the form and the functioning of 

 plant structures and plants as a whole. 



PHYSIOLOGY. 



Plant physiology began to take form in America about the 

 beginning of our period, 1890. and many of its problems are 

 unsolved. We know a good deal regarding fundamentals such 

 as carbon assimilation, the nature of foods, the chemical elements 

 and compounds necessary for their synthesis, the manner of 

 diffusion and transport of food materials and foods within the 

 plant, the formation of amides and ])roteids, nitrogen assmiila- 

 tion, the eft'ects of stimuli on plants, the nature and activities of 

 protoplasm, plant physics and chemistry, and some other prob- 

 lems. About none of these, however, have we complete knowl- 

 edge, and we know but little regarding some of them. 



We know that chlorophyllous plants utilize light in the manu- 

 facture of foods ; but we do not know whether these or non- 

 chlorophyllous plants make further use of radiant or obscure 

 heat in manufacturing amides and proteids. Nor do we know- 

 why certain hydrocarbons have greater food value, others less, 

 and still others perhaps none whatever. The part played by 

 enzymes in breaking down complex hydrocarbons in nutrition is 

 .still to be ascertained. In short, few of the problems of photo- 

 synthesis, proteinsynthesis, transfer, digestion, or assimilation are 

 finally settled. Nitrogen assimilation is a problem of profound 



