THE PHYSIOLOGY OF PITCHER-PLANTS. 



99 



bability that they all feed on the products of decomposition ; but 

 as yet we are absolutely ignorant whether the glands within the 

 pitchers are secretive or absorptive, or both ; if secretive, 

 whether they excrete water or a solvent ; and if ab- 

 sorptive, whether they absorb animal matter or the pro- 

 ducts of decomposition." Some years later, Schimper (" Bot. 

 Zeitung," 1882) made some observations like those of 

 Mellichamp and with the same results, and adduces evidence 

 to show that the products of decomposition are, as a matter of 

 fact, absorbed by the pitchers. Finally, Goebel has recently come 

 to the same conclusion (" Pflanzenbiologische Schilderungen," 

 ii. 1891, p. 166), partly on account of experiments with S. illus- 

 trata (a hybrid between S. flava and S. purpurea), and partly on 

 anatomical grounds. 



If any further evidence is needed to prove that the pitchers 

 of Sarracenia are organs for the capture of insects, it is 

 afforded by the anatomical features presented by their internal 

 surface. Generally speaking, this surface presents the following 

 varieties of structure: — The "hood" bears a few scattered 

 downwardly directed hairs, and, especially towards its lower part, 

 a number of glands which secrete honey. Next to this is a 

 smooth slippery surface, which extends for a short distance 

 below the orifice of the pitcher ; this is followed by a much 

 longer region bearing stiff hairs pointing downwards, amongst 

 which are some glands ; and towards the bottom of the pitcher 

 the hairs cease and the surface is smooth. This arrangement 

 produces an admirable insect- trap. Insects are attracted to the 

 mouth of the pitcher by the honey secreted about it ; they slip 

 on the smooth surface upon which the honey-glands border and 

 fall down in among the hairs below, which offer an almost in- 

 superable obstacle to their climbing out again. 



To summarise what has been said as to the function of the 

 pitchers of Sarracenia, it is evident that they are undoubtedly 

 organs for the capture of insects, and it is equally clear that the 

 captured insects contribute to the nutrition of the plant. It is 

 also most probable that the insects undergo decomposition and 

 not digestion ; for there do not appear to be any glands in the 

 pitchers to secrete a digestive enzyme ; and, moreover, many 

 observers have noticed the presence of living maggots in the 

 pitchers which would be impossible were a digestive liquid 



H 2 



