646 STIMULUS-TRANSMITTING SYSTEM 



travels at the rate of no less than 100 mm. per second. Linsbauer's 

 results stand in need of confirmation, especially as his methods 

 involve the risk of a variety of errors. 



If the author's theory of stimulus-transmission in Mimosa pudica 

 is correct, a shock or wound-stimulus should only be propagated in 

 organs which contain the special transmitting elements that is to 

 say, in the leaves and stems, and in the main root. According to the 

 author's observations (which conflict with those of Borzi), section of 

 lateral roots (even where these are of the first order) never provokes 

 any movement of the leaves ; this result is significant in view of 

 the fact that the cells to which the transmitting function has been 

 ascribed are entirely absent from the lateral roots. 346 



It may be presumed that the mechanism of transmission which 

 occurs in Mimosa pudica, also prevails in the remaining sensitive 

 species of the genus (M. sensitive/,, M. Spegazinii, M. casta, M. viva, 

 etc.), as well as in the other Leguminosae which exhibit the same 

 peculiar form of irritability (Smithia sensitiva, Acschynomcnc sensitiva, 

 A. indica, A. pumula, Desmanthus stolonifer, etc.). 



In conclusion, reference may be made to the fact that the stimulus- 

 conducting cells of Mimosa, pudica, though located in the leptome, do 

 not stand in any direct phylogenetic relation to sieve-tubes ; they 

 are, on the contrary, homologous with certain excretory sacs which are 

 of very general occurrence among the Leguminosae, where they 

 frequently take the form of tannin-sacs associated with the leptome- 

 strands (e.g. in Phascolus multifiorvs, Bobinia pscudacacia, etc.). 



