86 DROSEEA ROTUNDIFOLIA. Chap. VI. 



It may be well to premise for the sake of any reader 

 wlio knows nothing about the digestion of albuminous 

 compounds by animals that this is effected by means 

 of a ferment, pepsin, together with weak hydrochloric 

 acid, though almost any acid will serve. Yet neither 

 pepsin nor an acid by itself has any such power.* 

 We have seen that when the glands of the disc are 

 excited by the contact of any object, especially of 

 one containing nitrogenous matter, the outer ten- 

 tacles and often the blade become inflected ; the leaf 

 being thus converted into a temporary cup or sto- 

 mach. At the same time the discal glands secrete 

 more copiously, and the secretion becomes acid. 

 Moreover, they transmit some influence to the glands 

 of the exterior tentacles, causing them to pour forth 

 a more copious secretion, which also . becomes acid or 

 more acid than it was before. 



As this result is an important one, I will give the 

 evidence. The secretion of many glands on thirty 

 leaves, which had not been in any way excited, was 

 tested with litmus paper ; and the secretion of twenty- 

 two of these leaves did not in the least affect the colour, 

 whereas that of eight caused an exceedingly feeble 

 and sometimes doubtful tinge of red. Two other 

 old leaves, however, which appeared to have been in- 

 flected several times, acted much more decidedly on 

 the paper. Particles of clean glass were then placed 

 on five of the leaves, cubes of albumen on six, and 

 bits of raw meat on three, on none of which was the 

 secretion at this time in the least acid. After an 

 interval of 24 hrs., when almost all the tentacles on 



* It appears, however, accord- though slowly, a very minute 



ing to Schilf, and contrary to tho quantity of coagulated albumen., 



opinion of some physiologists, 8chitf, 'Phys. de la Digestion,' 



that weak liydrochloric dissolves, torn. ii. 1867, p. 25. 



