THE PHYSIOLOGY OF PITCHER-PLANTS. 



109 



Buitenzorg," III., 1882), whereas in most pitchers the internal 

 surface corresponds to the superior or ventral surface of the leaf, 

 in Dischidia (as also in Lathraea), the internal surface cor- 

 responds to the inferior or dorsal surface of the leaf. Moreover 

 the pitcher presents none of those peculiarities of structure in 

 its interior which make the pitchers of these other genera such 

 efficient insect-traps ; here are no glands, either digestive or 

 secreting honey, nor any hairs to prevent the exit of animals 

 which may have found their way into the pitchers ; on the 

 contrary, the internal surface of the pitcher is quite smooth, 

 consisting of an epidermal layer of cells with highly cuticularised 

 walls, among which are numerous stomata. 



As to the contents of the pitchers, although Griffith says 

 ("Trans. Linn. Soc," xx., 1851), "they appear at no period to 

 contain fluids," they have generally been found to contain water, 

 as also small quantities of earth, fragments of leaves, &c, forming 

 a rich soil. However, the contents of a pitcher will naturally 

 depend upon its position ; and as the pitchers of Dischidia take 

 up all possible positions, so that the orifice may be directed 

 upwards, or downwards, or horizontally, the foregoing statement 

 obviously applies more particularly to pitchers hanging with the 

 orifice upwards. But the most striking feature in the economy 

 of this plant is the fact that each pitcher contains an adven- 

 titious root which springs generally from the stalk of the pitcher 

 itself. 



Now as to the function of these pitchers. On this point 

 Wallich (" PI. Asiat. Bar.," vol. 2, p. 142, 1831) says:— "I am 

 unable to offer any conjecture as to the immediate use of these 

 curious reservoirs, unless it be to protect the tender roots which 

 are always found in them in great luxuriance ; for after con- 

 tinuing a certain time, the bags acquire a yellowish hue and 

 gradually decay, leaving the roots to attach themselves to the 

 trunk of the tree on which the plant grows. . . . The bags contain 

 generally a great number of small and harmless black ants, 

 most of which find a watery grave in the turbid fluid which 

 frequently half fills the cavity, and which seems to be entirely 

 derived from without." Unger, on the other hand, considers 

 that the liquid is secreted by the plant itself (" Anat. und 

 Physiol.," 1855, pp. 214, 358); and Delpino suggests (" Nuovo 

 Giorn. Bot. Ital.," hi., 1871 ; " Malpighia," iv., 1890) that these 



