A QUARTER-CENTURY OF PLANT PHYSIOLOGY 11 



study sugar solutions in distilled water or to use purified chemi- 

 cals of any kind? 



Now, if we wish to find out what chemical conditions are best 

 suited to the development of plants it has long been our practice 

 to control the chemical surroundings of our experimental cul- 

 tures, and we have usually allowed the climatic conditions to 

 fluctuate as they would. A very carefully selected plant may 

 be placed in a very carefully washed Jena-glass jar of a very 

 carefully prepared nutrient solution and the culture may be 

 placed, forsooth, in a north window or in a well-lighted greenhouse! 

 This anti-climax suggests the burden of my present plea. Our 

 experimentation is of relatively little value, and we may know 

 that it will soon be all to do over again, so long as we do not 

 attend to the aerial environment of our experimental plants 

 as thoroughly as we do to the nutrient media and the internal 

 conditions as represented by pure strains, similar seeds, and so 

 forth. 



Obviously, what is needed is properly equipped laboratories, 

 where climates may be made to order as truly as soil solutions 

 are now commonly made. Such laboratories cannot be arranged 

 with slight expenditure in rooms of an architect's building; they 

 must be planned from the ground up, or rather, from the ground 

 down, for I suspect they will be underground, for easy climatic 

 control. A greenhouse used to be what the experimental phys- 

 iologist first asked for, in the future he will demand elaborately 

 equipped chambers, thoroughly protected from the influence 

 of natural conditions. The physical sciences have now placed 

 in our hands all the equipment for such culture chambers, and 

 what we have to do is simply to adapt and arrange such equip- 

 ment. For more than a decade I have watched the improvement 

 in electrical devices for producing light, with the idea that these 

 were the only instz'uments not already suited to our purposes. 

 Very recently the production of nitrogen-filled incandescent 

 lamps has practically filled this gap. The enclosed mercury 

 arc has been available for a longer time and has actually been 

 employed in physiological studies. Temperature and humidity 

 control are now fairly simple; the arrangements for these, as 



