Chapter IV — 69 — Nepenthes 



showed that nitrogen, as ammonia and peptone, is rapidly reabsorbed 

 (1891). 



Concerning the overhanging eave-like coverings of the glands, 

 Knoll argued that they serve to prevent the use of the gland for foot- 

 hold by insects, but incidentally prevent also damage by their claws to 

 the glands themselves. 



Digestion. — The students of digestion in Nepenthes (as in other 

 insectivorous plants) have been divided into two camps {a) of those 

 who argued that it is a function of the plant itself carried out by the 

 secretion of an appropriate enzyme and {b) of those who have believed 

 it to be the result of bacterial action (decay or rotting, Dubois). If 

 the latter only takes place (as seems to be true in Darlingtonia, Hel- 

 iamphora, and perhaps some spp. of Sarracenia) this fact does not 

 disqualify these as carnivorous; bacterial action is an invariable ac- 

 companiment of some animal digestion {e.g. of cellulose in herbivores). 

 Bacterial action is often unavoidable in open pitchers and it has not always 

 been possible to separate the different digestive processes. Nepenthes 

 offers a special condition in that the pitchers secrete a quantity of fluid 

 before they open. The nature of this fluid was investigated by Voel- 

 KER (1849). He described it as hmpid and colorless, with a slight 

 agreeable odor and taste, and containing a non-volatile acid. The 

 total solids in percentage of the fluid ranged from 0.27 to 0.92 of 

 which 63.94% to 74.14% was non-volatile substances. Potassium, 

 sodium, magnesium, calcium, chlorine (as hydrochloric acid) and 

 organic acids were found, chiefly malic, with a little citric. Tait 

 found that pitcher fluid from unopened pitchers was sometimes acid, 

 but frequently not. When flies had found their way into open pitchers 

 the fluid became much more acid as well as more viscid. According 

 to VON GoRUP and Will (1876) the fluid is colorless, clear or slightly 

 opalescent, odorless, tasteless and of various consistency. After stimu- 

 lation the fluid changes from being neutral or only slightly acid, to 

 decidedly acid. "Miss R. Bok found that carefully washed beakers 

 of Nepenthes filled with distilled water did not show any acid pro- 

 duction while the addition of 2o/mgr./liter NH4CI would cause prompt 

 acid production. The pH went down to about 3.0 in 24 hours". 

 (Baas Becking, in ep.). 



It is an important and well attested fact that the fluid of unopened 

 pitchers is above all free of bacteria, owing in part to the tight sealing 

 around the edge of the lid by interwoven branching hairs, a precursor 

 in Nature of the cotton plug used in bacteriological technique. 



The pioneer work, constituting a prime stimulus to the investiga- 

 tion of digestion in carnivorous plants, was done by J. D. Hooker, 

 announced in his address before the Biological Section of the British 

 Association for the Advancement of Science in August 1874. Hooker 

 was in touch with Charles Darwin, and his interest was a natural 

 outcome of this contact; for Darwin was finishing his book on car- 

 nivorous plants at the time. Hooker found that bits of egg-white, 

 meat, fibrin and cartilage, when placed in the pitchers, showed un- 

 mistakable evidence in 24 hours of disintegration, but that this action 

 was by no means so pronounced in fluid placed in test tubes. From 

 this Hooker inferred that the digestion depends not on the first fluid 



