18 DROSERA ROTUNDIFOLIA. [Chap. I. 



secretion. I ascertained this by selecting leaves with equal- 

 sized drops on the two sides, and by placing bits of meat on 

 one side of the disc; and as soon as the tentacles on this side 

 became much inflected, but before the glands touched the 

 meat, the drops of secretion became larger. This was re- 

 peatedly observed, but a record was kept of only thirteen 

 cases, in nine of which increased secretion was plainly ob- 

 served; the four failures being due either to the leaves being 

 rather torpid, or to the bits of meat being too small to cause 

 much inflection. We must therefore conclude that the cen- 

 tral glands, when strongly excited, transmit some influence 

 to the glands of the circumferential tentacles, causing them 

 to secrete more copiously. 



It is a still more important fact (as we shall see more fully 

 when we treat of the digestive power of the secretion), that 

 when the tentacles become inflected, owing to the central 

 glands having been " stimulated mechanically, or by contact 

 with animal matter, the secretion not only increases in quan- 

 tity, but changes its nature and becomes acid; and this oc- 

 curs before the glands have touched the object on the centre 

 of the leaf. This acid is of a different nature from that con- 

 tained in the tissue of the leaves. As long as the tentacles 

 remain closely inflected, the glands continue to secrete, and 

 the secretion is acid; so that, if neutralised by carbonate of 

 soda, it again becomes acid after a few hours. I have ob- 

 served the same leaf with the tentacles closely inflected over 

 rather indigestible substances, such as chemically prepared 

 casein,* pouring forth acid secretion for eight successive days, 

 and over bits of bone for ten successive days. 



The secretion seems to possess, like the gastric juice of 

 the higher animals, some antiseptic power. During very 

 warm weather I placed close together two equal-sized bits of 

 raw meat, one on a leaf of the Drosera, and the other sur- 

 rounded by wet moss. They were thus left for 48 hrs., and 

 then examined. The bit on the moss swarmed with infusoria, 

 and was so much decayed that the transverse stria3 on the 

 muscular fibres could no longer be clearly distinguished; 

 whilst the bit on the leaf, which was bathed by the secretion, 

 was free from infusoria, and its strias were perfectly distinct 



[These obBervntlooH are not of preparation of the casein. See 

 truBtwortbjr, owing to the mode p. 65. F. D.] 



