BY A. G. HAMILTON. 51 



the lid in veiy young pitchers, and so prevent the ingress of 

 insects when their presence would be undesirable. But again 

 this does not account for their downward production. The lid 

 probably acts as a cover against rain, but it also prevents insects 

 jumping or flying out, and it has been suggested that the trans- 

 parent windows are designed to cause the insect to fly upwards 

 and be stopped, instead of escaping laterally between the rim 

 and the lid. The recurved teeth and the collar act as the 

 recurved tips in a lobster-pot in preventing exit. The collar acts 

 in the same way as a similar ledge does in a safety ink bottle — 

 it prevents the liquid running out when the pitcher is turned 

 upside down. A pitcher containing the normal amount of fluid 

 lets very little escape when inverted. Insects visiting the pitcher 

 delay a long time licking the surface of the collar before proceed- 

 ing lower. The fine hairs on the under surface of the lid and on 

 inside of collar are said to prevent insects from crawling up, but 

 they are so very minute that I imagine only very small insects 

 could be stopped by them, unless indeed by getting into the 

 joints of the feet they cause discomfort, or clog their steps. There 

 is no doubt, however, that they facilitate the downward passage 

 of the victim. Below the collar extends the ver}^ slippy glandular 

 and eglandular surface, and here the purpose is obvious. Small 

 insects cannot get up it, especially when wet. In some of my 

 plants I found, before the liquid appeared, live harvest-bugs, both 

 crimson and black, and the larger ones could come out at will. 

 Probably man}' of the victims go into the pitchers as a hiding 

 place. 



The purpose of the fluid is a problem worth investigating. 

 Two views are taken : First, that it is merely a culture fluid for 

 bacteria which dissolve or decompose the captives, and so render 

 them available as food for the plant. The pepsin which has been 

 detected in the liquid of some pitchers is said to be derived from 

 the bacteria. In this case there would be a true instance of 

 symbiosis between a high plant and a very low one (11, 12, 13). 

 But this view has been ably combated by Yines (14), whose 

 experiments, made under conditions excluding the action of 



