110 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



pitchers, like those of Sarracenia, are traps for catching insects 

 which, on decomposition, afford nutriment to the plant. There 

 is, however, no sufficient ground for regarding the pitchers 

 either as secretory organs or as insect-traps ; on the contrary, 

 the structure of the internal surface conclusively proves that 

 the pitcher can neither secrete nor absorb, and that it is ill- 

 adapted for the capture of insects. Treub points out (" Ann. du 

 Jard. Bot. de Buitenzorg," III., 1882) that the liquid is cer- 

 tainly not secreted by the plant, but is merely rainwater, and 

 concludes that the main object of the pitchers is to economise 

 water in view of the dry habitat of these plants. The pendent 

 pitchers, with the orifice upward, serve to collect rainwater, 

 which can be absorbed by the roots entering each pitcher ; the 

 inverted pitchers cannot collect rainwater, but serve to condense 

 the watery vapour given off by transpiration through the 

 numerous stomata on their internal surface, and thus they 

 render it available for re-absorption by the roots ; the oblique 

 or horizontal pitchers discharge one or both of these functions in 

 varying degree according to their position. The detritus which 

 collects in the pendent pitchers — apparently often carried thither 

 by ants — no doubt affords nutritive material which is absorbed 

 by the roots. These views have been confirmed by the recent 

 observations of Groom and of Scott and Sargant (" Annals of 

 Botany," vii., 1893). Hence these pitchers differ essentially in 

 function from all those which we have considered, in that they 

 are primarily organs for maintaining the water-supply of the 

 plant. 



In conclusion we may briefly review the main facts which 

 have been ascertained. We find, in the first place, that the 

 great majority of these pitchers are "insect-traps" (Sarrace- 

 niaceao, Nepenthes, Cephalotus, Utricularia, Genlisea) ; whilst 

 the others (Lathraoa, Dischidia) have, apparently, no relation to 

 the capture of animals. Of the 11 insect-traps," the majority 

 appear to be incapable of digesting the animals which they 

 capture (Sarraceniacea;, Utricularia, Genlisea), absorbing merely 

 the products of decomposition effected by micro-organisms ; so 

 that these plants are not really "carnivorous," but only sapro- 

 phytic : on the other hand, the pitcher of Nepenthes, and perhaps 

 that of Cephalotus, undoubtedly secretes a digestive enzyme, so 

 that the former genus, at any rate, is truly " carnivorous." Those 



