252 Scott and Sargant . — On the Pitchers of 
The structure of the petiole of pitcher and leaf is essentially 
the same. The meristele of the pitcher is the larger and its 
xylem very much more abundant, as we should expect from 
the much greater size of the organ to be supplied. In the 
petiole of the leaf the meristele is slightly concave towards the 
upper surface ; in that of the pitcher the curvature is much 
more marked. 
It is interesting to find that in the pitcher-petiole there is 
an active cambium between the xylem and the normal phloem, 
by which new elements are continually added to both tissues, 
the older phloem-elements consequently becoming obliterated. 
There is also a cambial increase of the superior or internal 
phloem, with resulting obliteration. Nothing of this kind 
occurs in the petiole of the ordinary leaf. This difference is 
evidently correlated with the long duration of life of the 
pitchers as contrasted with the transitory existence of the very 
caducous leaves. 
The Purple Coloration of the Inner Surface of 
the Pitcher. 
This was especially studied in the specimens from Burmah. 
The pigment was very well developed, giving the inside of the 
pitcher a fine deep purple colour, contrasting strikingly with 
the pale green of the outer surface. The pigment, which is in 
solution in the cell-sap, is limited to a thin layer of the 
mesophyll next the inner surface. 
The spectrum of the light transmitted through the pigment 
was observed by means of a Zeiss micro-spectroscope. 
Observations were first made on the whole thickness of the 
pitcher-wall, in order to determine the character of the light 
which actually reaches the interior of the pitcher through its 
wall, in nature. The light which penetrated the thick mass of 
tissue was however too faint for spectroscopic analysis. 
Next, the thin purple inner layer was cut away from the 
thicker outer green layer, and each examined by itself. The 
intensity of the light passing through the green and red layers 
appeared to be about equal, notwithstanding their great differ- 
