2i6 PLANT PHYSIOLOGY 



for the study, the Horse Bean shows the most active movement, though 

 for a combination of rapidity, amplitude, and frequency of change of direc- 

 tion, the Radish is best of all. Then follow in order Fuchsia, Grape Hya- 

 cinth, Sunflower, Ficus, and Oats. 



DEMONSTRATION METHODS. Circumnutation, it is true, is a phenome- 

 non of no great physiological importance, but it is worth some emphasis in 

 an experimental course because it is always a matter of general interest, 

 and, moreover, it involves some very exact manipulation which affords 

 valuable training even to comparatively young students. I find the method 

 above described, using the apparatus of figure 58, very satisfactory. 



The student should now, by aid of the literature, extend his 

 study of this subject to an understanding of our knowledge of 

 the nature and meaning of Circumnutation (which would better 

 be called Nutation) in relation to Growth, together with other 

 autonomic growth movements. Especially he should make some 

 study of DARWIN'S book, "The Power of Movement in Plants." 



The consideration of Nutation leads to the inquiry whether 

 other movements exist, likewise dependent upon internal, rather 

 than external, factors. Several of these do occur, and (aside 

 from the anomalous spontaneous movements of the leaflets of 

 Desmodium gyrans] are mostly of much importance to the assump- 

 tion of its form by the plant. These include epinasty, hypo- 

 nasty, and, under exceptional conditions, rectipetality (or auto- 

 Iropism). Of another kind, though also belonging here, are 

 polarity, some phases of regeneration, and Sachs' curvature. All 

 of these are susceptible of ready observational or experimental 

 study, and the student may follow them, if he will, by aid of the 

 excellent directions given by DETMER, to which I am unable 

 to add anything from my own experience. Many other growth 

 movements there are, but these depend upon external stimuli, 

 and hence their study belongs under Irritability later. 



There still remain some special topics of more or less impor- 

 tance which, however, the student may most profitably work 

 up through the literature. They include resting periods (and 

 the relation thereto of enzymes}, rhythms, and periodicity (espe- 

 cially striking in the vegetation of temperate climates), contrac- 

 tions during the growth of some roots, and a relation between 

 transpiration and growth whereby one may to some extent be 



