204 DROSERA ROTUNDIFOLIA. [Chap. X. 



disc, for instance near the extremities of the sublateral 

 bundles (Fig. 11), which are supplied with vessels that do not 

 come into contact with the branches that enter the sur- 

 rounding tentacles, except by a very long and extremely cir- 

 cuitous course. Nevertheless, if a bit of meat is placed on 

 the gland of a tentacle of this kind, all the surrounding ones 

 are inflected towards it with great precision. It is, of 

 course, possible that an impulse might be sent through a 

 long and circuitous course, but it is obviously impossible 

 that the direction of the movement could be thus communi- 

 cated, so that all the surrounding tentacles should bend 

 precisely to the point of excitement. The impulse no doubt 

 is transmitted in straight radiating lines from the excited 

 gland to the surrounding tentacles; it cannot, therefore, be 

 sent along the fibro-vascular bundles. The effect of cutting 

 the central vessels, in the above cases, in preventing the 

 transmission of the motor impulse from the distal to the 

 basal end of a leaf, may be attributed to a considerable space 

 of the cellular tissue having been divided. We shall here- 

 after see, when we treat of Dionsea^ that this same conclu- 

 sion, namely that the motor impulse is not transmitted by 

 the fibro-vascular bundles, is plainly confirmed; and Pro- 

 fessor Cohn has come to the same conclusion with respect to 

 Aldrovanda both members of the Droseracese.* 



As the motor impulse is not transmitted along the ves- 

 sels, there remains for its passage only the cellular tissue; 

 and the structure of this tissue explains to a certain extent 

 how it travels so quickly down the long exterior tentacles, 



[Bntnlln (' Flora,' 1877) ex- siipKostod that In the case of 



perlniented on the transmission MasdrraUia muscona the Impulse 



of the motor Impnise, and con- travels In a sheath of thin walled 



firms the observations of Zlejjler pareiK'hyma afOonipanylnK the 



('<'ompto8 rendus,' 1874), from xyleni. If we make a similar as- 



whleh that nattirallst concluded sumption for Drosera, we should 



that the vascular bundles form pet rUI of a difflculty, for whcth- 



the path for the transmission of er the Impulse travels In the 



the Impulse. Katalln concludes course of the vascular bundles or 



that Impulse travels with far transversely across the leaf. It 



jrreater ease aloni; the vessels would In either case be travel- 



than across the parenchyma, and llnj? In parenchymatous tissue; 



that the course of the stlmtilus the only difference between the 



Is normally almost exclusively two cases bclnic that the paren- 



alunK the vessels. ohyma aceompanyInK the vessels 



If wo believe that the motor would be specially adapte<l for 



Impulse travels ns n molecular rapid transmission In a definite 



chanKe In the protoplasm, we direction, whereas the ordinary 



cannot suppose that it travels In narencbyma has to transmit the 



the trachelds. Now Oliver (* An- impulse In a variety of dlrec- 



nals of Botany,' Feb. 1888) has tiuus. F. D.] 



