204 A NATURALIST IN BORNEO 



in the water contained in the pitchers of D. rafflesiana 

 and D. shelfordi, is indeed infinitesimal. As pointed 

 out in a previous chapter, terrestrial insects take an 

 unconscionably long time about dying from drowning, 

 and, owing to the numerous rootlets in the pitchers, 

 they have an easy means of exit when their quarters 

 become flooded. I feel convinced that it will event- 

 ually be shown that the inner pitchers are designed 

 for the purpose of producing a food-substance attrac- 

 tive to ants ; the sweet decomposition products already 

 mentioned may be the pathological results of ant- 

 punctures, but they may also be normal katabolic 

 changes, whilst the presence of numerous gland-cells 

 in the inner pitcher walls points to the conclusion 

 that these too may secrete a substance palatable to 

 ants. 



In conclusion, it is reasonable to regard the pitchers 

 of D. shelfordi as developed with a double purpose 

 to store water and protect rootlets, and to attract and 

 shelter ants. They thus differ from such simple 

 structures as the hollow stem of Macaranga caladi- 

 folia, punctured casually by ants, and from all 

 accidental ant-shelters ; they differ, too, from the 

 remarkable tubes of Myrmecodia and the swollen 

 rhizomes of Polypodium carnosum, which are developed 

 to harbour ants at least inconvenience to the plants ; 

 and they differ, too, from those structures which are 

 developed purely for attraction of ants, as the thorns 

 on the Neotropical Acacia cornigera. In fact, they 

 take their place in a long series leading from simple 

 beginnings to complex endings. To assert, as some 

 have done, that all " myrmecophilous " plants derive 

 great benefit from their association with ants, and 



