Chap. VI.] DIGESTION. 73 



them was likewise strongly acid. As raw meat moistened 

 with water is slightly acid, I compared its action on litmus 

 paper before it was placed on the leaves, and afterwards when 

 bathed in the secretion; and there could not be the least 

 doubt that the latter was very much more acid. I have in- 

 deed tried hundreds of times the state of the secretion on 

 the discs of leaves which were inflected over various objects, 

 and never failed to find it acid. We may, therefore, conclude 

 that the secretion from unexcited leaves, though extremely 

 viscid, is not acid or only slightly so, but that it becomes 

 acid, or much more strongly so, after the tentacles have be- 

 gun to bend over any inorganic or organic object; and still 

 more strongly acid after the tentacles have remained for 

 gome time closely clasped over any object. 



I may here remind the reader that the secretion appears 

 to be to a certain extent antiseptic, as it checks the appear- 

 ance of mould and infusoria, thus preventing for a time 

 the discoloration and decay of such substances as the white 

 of an egg, cheese, &c. It therefore acts like the gastric 

 juice of the higher animals, which is known to arrest putre- 

 faction by destroying the microzymes. 



As I was anxious to leam what acid * the secretion contained, 445 

 leaves were washed in distilled water, given me by Professor Frank- 

 land; but the secretion is so viscid that it is' scarcely possible to 

 scrape or wash off the whole. The conditions were also unfavour- 

 able, as it was late in the year and the leaves were small. Pro- 

 fessor Frankland with great kindness undertook to test the ffuid 

 thus collected. The leaves were excited by clean particles of glass 

 placed on them 24 hrs. previously. No doubt much more acid would 

 have been secreted had the leaves been excited by animal matter, 

 but this would have rendered the analysis more difficult. Professor 

 Frankland informs me that the fluid contained no trace of hydro- 

 chloric, sulphuric, tartaric, oxalic, or formic acids. This having been 

 ascertained, the remainder of the fluid was evaporated nearly to dry: 

 ness, and acidified with sulphuric acid ; it then evolved volatile acid 



* [Messrs. Rees and Will the evidence of the smell. Gornp 



(' Bot. Zeltnng,' 1875, p. 716) and Will have shown that the 



stimulated the glands of some nentral secretion of Nepenthes 



thousand Drosera plants with becomes powerfully digestive 



glass-dust and analysed the se- when aclanlated with formic 



cretion thus produced. Thoy acid (see ' Bot. Zeltung,' 1870, p. 



found a variety of fatty a'id8 470). It Is therefore Interesting 



present, among which Formic to find this noid naturally pres- 



acld was recognised with cer- ent In the secretion of Drosera. 



talnty, and Propionic and Bu- F. D.] 

 tyric adds were suspected from 



