258 The Plant World. 



The first critical study of the question of transmission of 

 the stimulus in these plants was made by Oliver f. the species 

 receiving attention being Mimulus cardinalis, M. luteus, Mar- 

 tyma lutea and M. proboscidia. Oliver's purpose was to deter- 

 mine the path of transmission of the stimtilus from one stigma- 

 lip to the other, since, according to him, this occurs in all these 

 species except in Mimulus luteus, in which the stimulus is not 

 so transmitted. This I am able to confirm. 



By a nice method of excising a portion of the vascular 

 tissue from one lip, it was proved by Oliver that there was no 

 hindrance to the transfer of the stimulus to the other, thereby 

 showing that, in these forms, the path of transmission lies in the 

 parenchyma. Oliver believed that this is made possible by the 

 presence of protoplasmic continuity, a conclusion which seems 

 reasonable, but not yet demonstrated to be true. The immedi- 

 ate cause of the movement of the stigma lip this author finds in 

 the movements of water into the intercellular spaces, the pres- 

 ence of which has been previously denied by Kabsch J and by 

 E. Heckel * and affirmed by Mitchell* with whom Oliver proper- 

 ly agreed. Oliver's description of the structure of the stigma- 

 lip appears to be applicable to Diplacus except for a slight and 

 not important omission, namely that the epidermis of the outer 

 face is relatively quite thick, and has in the absence of turgor in 

 the motile tissue a considerable power of recovery when bent 

 away from the plane of the style. * f 



Burck * studying Torenia fournieri and Mimulus luteus. 

 found that the presence of appropriate pollen causes the stigma 

 to remain closed, the closure following mechanical stimulus. This 

 work will be referred to more specifically beyond. 



THE NATURE OF THE STIMULUS 



Under normal conditions the entrance of a large enough 



♦Oliver, F. W. Ueber Fortleitung des Reizes bei reizbaren Narben. Ber. d. D. Bot. 

 Gesellsch. 5: 162-169. 1887. 



*Kabsch W. Uber die Einwirkung der gase usw. Bot. Zeitung, 1862, p. 341. (through 

 Correns 1. c.) 



* *Du inouvement vegetal, Paris, 1875, p. 89 (through Oliver). 



t tArchives des sc. phys. et nat. de Geneve, 15 Feb. 1875 (through Oliver). 



fOn the importance of similar mechanical tissue, but of greater extent, in the motile stamens 

 of Berheris and Centaurea see .Tuel, H. O., Einige Beobachtungen an reizbaren Staubfaden . 

 Bot Stud, tillagn, F. R. Kjellman, 1906. 



*tBurck, W. On the irritable stigmas of Torenia Foiirtiieri and Mimulus Culeus and on 

 means to prevent the germination of foreign pollen on the stigma. Proc. Kon. Akad. v. 

 Wet. te Amst. Sept. 20, 1901. (Ref. in Bot. Central) bl. 89 (No. 23) 645. 1902. 



