Geology and Natural History. 189 



universal ; according to the author, wherever there is a living 

 tissue, no matter how sluggish it may seem, response may be 

 elicited by appropriate means. There are certain conditions 

 which are conspicuously favorable to the exhibition of mechani- 

 cal response, and these conditions have been carefully studied. 

 Such study has convinced the author that there is no difference, 

 except in degree, between the ordinary and the so-called sensitive 

 plants. The mechanical response in ordinary leaves and the lon- 

 gitudinal response of radial organs have been examined in detail 

 by means of newly-devised apparatus, which appears to possess 

 the power of recording even the slightest possible movement 

 after stimulation of the plant or its parts. The responsive curva- 

 ture of molecularly anisotropic organs receives a good deal of 

 attention, and the complex phenomena are resolved into their 

 simpler terms or factors. Lastly, under this heading, comes the 

 consideration of the relation between stimulus and response, and 

 also, the effect of the superposition of stimuli. Here tetanus in 

 plants is described. 



In Part 2d the author treats of the modification of response 

 under various conditions. Here are studied the theories concern- 

 ing different types of response, the effects of anaesthetics, poisons, 

 and other chemical agents on longitudinal response. The effects 

 of temperature receive attention in a special chapter, as does also 

 the "death-spasm" in plants. The critical point of death is 

 determined by inversion of the thermo-mechanical curve. In 

 connection with this topic the author examines at considerable 

 length the subject of local fatigue and regional death. 



Excitability and conductivity are considered in Part 3. Polar 

 effects, electrotonus, electrotactile and electromotive methods, 

 and the latent as well as the " refractory " periods are fully 

 treated of. Then follows the consideration, in part 4, of multiple 

 and autonomous response ; and the similarities of rythm in ani- 

 mals and plants are clearly stated. The ascent of sap and the 

 general subject of growth are next presented, and the supposed 

 relations of both to certain stimuli are insisted upon. Following 

 come Geotropism, Chemotropism, and Galvanotropism. Near the 

 close of the last chapter in this part the author considers the 

 effect on growth of " electrification " of the soil. To the subject 

 of Heliotropism the author devotes the whole of part 8. He takes 

 up even the effect of invisible radiation and the action of the 

 high frequency Tesla current. Torsional response receives a fair 

 share of attention. Besides this is considered the topic of pulsa- 

 tory response and the swimming movements. 



Part 9 concludes the treatise with general reviews and a final 

 examination of the continuity of physiological response in plant 

 and animal. Three features render this work of great interest: 

 (1) the summaries at the close of the chapters, (2) the descrip- 

 tions of entirely new types of delicate apparatus, and (3) the fact 

 that the greater part of the experiments were conducted under 

 the most favorable conditions in a tropical climate upon tropical 



