225 



demonstrations of physical principles were only less entertaining 

 than the monthly public declamations or the recitals of the banjo 

 club. 



It would seem to be folly to bar out from the laboratory work 

 in botany such studies as those on the blanching effect of cutting 

 off light from green portions of the plant body, because it is not 

 easy to express the effect in convenient units. So, too, it is well 

 worth while to have every student produce positive and negative 

 heliotropic movements in convenient portions of the plant body, 

 and yet it would be an unprofitable labor to determine exactly 

 what per cent, of the total sunlight is required to initiate such 

 movements. But even the beginner in botany (of high school 

 age) cannot get out of his subject nearly all that it can give him 

 unless he has made some careful quantitative studies, not all of 

 them necessarily physiological. For example, a few of the 

 topics which readily lend themselves to quantitative treatment 

 are : the relation of temperature to germination, to asexual repro- 

 duction (as in bacteria and yeasts), the percentage of water in the 

 plant body, the effect of lowered temperature on root absorption, 

 the approximate pressure of the root tip, the effectiveness of corky 

 epidermis in preventing evaporation, the relative transpiration rates 

 at various temperatures, critical temperatures and illuminations to 

 produce nastic movements of foliage leaves and floral leaves, the 

 minimum illumination for typical shade plants, and the number of 

 competitors on a unit area of weedy soil. If the teacher has not 

 had considerable practice in making quantitative studies of the 

 character of those here mentioned, he may find it highly profitable 

 to complete a goodly number of them and then endeavor to make 

 a statement of the comparative accuracy and vitality of his knowl- 

 edge of each topic before and after subjecting it to quantitative 

 investigation. 



If botany is to stand as an important subject in high school 

 courses it must claim a place there not only because it fosters a 

 love of nature and cultivates the esthetic sense — and these it 

 should do — but also because it affords training in careful ob- 

 serving and scientific thinking. Will the botany teacher who 

 objects to quantitative laboratory work be good enough to 



