134 PLANT PHYSIOLOGY. 



Relations of intensity of stimulus to amount of response ; 



Weber's law. 



Tonic, or formative, i's. directive effects. 

 Relation of responses to respiration and growth. 

 Correlations ; induction effects ; acclimatization to stimuli. 

 After-effects; reaction times ; latent periods ; rigors; rhythms. 

 Perceptive and motor regions in different organs ; transmission 



of stimuli. 

 Mechanisms which effect responses. 



LITERATURE. 



There is an immense literature on Irritability, which will 

 unquestionably be summarized in Vol. II of Pfeffer's Physiolo- 

 gic. Until the appearance of that work the subject may be 

 traced through the following: 



Pfeffer, W. Die Reizbarkheit cler Pflanzen. Leipzig, 1893. 

 Czapek, F. Writings upon Geotropism in recent volumes of 



Jahrbiicher fur wissenschaftliche Botanik. 

 Noll, F. Ueber Geotropismus. Jahrbiicher fur wiss. Botanik, 



34, 457- 

 Davenport, C. B. Comparative Morphology, Vol. II. 



Pfeffer, W. Geotropic Sensitiveness of the Root-tip. Annals 



of Botany, 8, 317. 

 Spalding, V. M. The Traumatropic Curvature of Roots. 



Annals of Botany, 8, 423. 

 Newcombe, L. C. The Regulatory Formation of Mechanical 



Tissue. Botanical Gazette, 2O, 441. 



Juel, H. O. Untersuchungen iiber Rheotropismus. Jahr- 

 biicher fiir wissenschaftliche Botanik, 34, 507. 

 Jost, L. Beitrage zur Kenntniss der nyctitropischen Bewe- 



gungen. Jahrbiicher fiir wiss. Botanik, 31, 345. 

 MacDougal, D. T. The Curvature of Roots. Botanical 



Gazette, 23, 307. 

 Mechanisms of Movement and Transmission of Stimuli in 



Mimosa and other Sensitive Plants. Botanical Gazette, 



22, 293. 



