528 'Journal of Comparative Neurology and Psychology. 



rotation of the fulcrum rod and of the mirror. A spot of Hght which is reflected 

 from the mirror is thereby caused to move. At a distance from the mirror which 

 is determined by the amount of magnification of the plant's movement which he 

 desires to obtain, the experimenter places a revolving drum on which he has 

 arranged a record sheet. As the spot of light moves over this sheet he traces its 

 course with a pen, or if he desires an automatic record he so arranges the mechanism 

 that a photographic record is made by the spot of light. This device in a highly 

 perfected and far more complex form than I have attempted to describe enabled 

 the author to obtain graphic records of extremely slight movements. 



In what he calls the "kunchangraph" (from the Sanskrit kunchan = contrac- 

 tion) BosE has a device which records the contractile response of the plant as the 

 myograph records that of the animal. The optical lever, for so the essential part 

 of the optical pluse-recorder is named, is employed in the kunchangraph. 



Largely through the use of the kunchangraph the author obtained the measure- 

 ments of the responses of a number of plants which constitute the basis for the 

 following conclusions. 



"The principal types of response seen in animal tissues are found also in the 

 responses of plants and of inorganic substances. 



"Three types of response are possible: (i) that in which response is propor- 

 tionate to stimulus; (2) that in which response is disproportionately greater than 

 stimulus; and (3) that in which all or part of the stimulus is, for a longer or shorter 

 time, absorbed by the tissue and held latent. 



"The subsequent effect of stimulus which is held latent may sometimes be 

 seen in singly ineffective stimulus which becomes effective on repetition; or in the 

 staircase response, consequent on the enhancing of molecular mobility by the 

 partial absorption of previous stimulus. 



"The fact that stimulus may be held latent for a time, and subsequently find 

 expression, is strikingly shown in the occurrence of multiple response, in answer 

 to a single strong stimulus. 



"It is also possible for the incident stimulus to become divided in its expression, 

 part of it finding an outlet directly in mechanical response, and part becoming 

 latent, and causing accelerated growth. . . ." (p. 128). 



I have quoted thus, from the summary of chapter nine, in order to exhibit the 

 kind of conclusions which BosE formulates in "Plant Response." 



Measurements of the velocity of transmission of excitatory, waves in plants indi- 

 cate that the rate varies between .5 and 14 mm. per second in different plants; that 

 the rate is not the same centripetally as centrifugally; that it increases with increas- 

 ing intensity of stimulus; that fibro-vascular bundles are the best channels of con- 

 duction; and that a refractory period is exhibited by plants. 



The author presents the results of a study of the eflFects of anaesthetics, poisons, 

 heat, cold, etc., on the various forms of plant response. Even to summarize his 

 results, as he has stated them, would lead us far beyond the limits of this review 

 notice. 



For his investigation of the ascent of sap, BosE invented the "shoshungraph" 

 (from the Sanskrit, shoshun = suction). It is a mechanism by means of which 

 changes in the amount of suction can be recorded on a revolving drum. As the 

 author states "It consists of (i) an arrangement by which the specimen may be 

 rapidly subjected to the action of different excitatory or depressing agents; (2) 



