Chap. XL GENEKAL SUMMAEY. 275 



ness of the leaves apj)ears to be wholly confined to 

 the glands and to the immediately underlying cells. 

 It was further shown that the motor impulse and other 

 forces or influences, proceeding from the glands when 

 excited, pass through the cellular tissue, and not along 

 the fibro-yascular bundles. A gland sends its motor 

 impulse with great rapidity down the pedicel of the 

 same tentacle to the basal part which alone bends. The 

 impulse, then passing onwards, spreads on all sides to 

 the surrounding tentacles, first affecting those which 

 stand nearest and then those farther off. But by being 

 thus spread out, and from the cells of the disc not 

 being so much elongated as those of the tentacles, it 

 loses force, and here travels much more slowly than 

 down the pedicels. Owing also to the direction and 

 form of the cells, it passes with greater ease and cele- 

 rity in a longitudinal than in a transverse line across 

 the disc. The impulse proceeding from the glands of 

 the extreme marginal tentacles does not seem to have 

 force enough to affect the adjoining tentacles ; and 

 this may be in part due to their length. The impulse 

 from the glands of the next few inner rows spreads 

 chiefly to the tentacles on each side and towards the 

 centre of the leaf ; but that proceeding from the glands 

 of the shorter tentacles on the disc radiates almost 

 equally on all sides. 



When a gland is strongly excited by the quantity 

 or quality of the substance placed on it, the motor 

 impulse travels farther than from one slightly excited ; 

 and if several glands are simultaneously excited, the 

 impulses from all unite and spread still farther. As 

 soon as a gland is excited, it discharges an impulse 

 which extends to a considerable, distance ; but after- 

 wards, whilst the gland is secreting and absorbing, 

 the impulse suffices only to keep the same tentacle 



