KRAMERIA CANESCENS. 21 
chlorophyll-bearing tissue is the subepidermal band which extends to the 
interrupted ring of hard bast. Chlorophyll is also to be found in the 
medullary rays and in the outer cells of the pith. 
The chlorophyll band is composed of a single layer of much-elongated 
palisade cells, or of a single layer of palisade cells and one tier of nearly 
cuboid cells which lie within, 7. ¢., towards, the woody cylinder. 
FIG. 9.—Krameria canescens: A, transverse section of leaf, showing char- 
acter of the subepidermal palisade cells; B, cross-section of stem, to show 
structure of cortical chlorophyll band; same magnification as in 4, ch. 6., 
cortical chlorophyll band; 2%. 4.,hard bast; med., medullary rays. 
With increase in diameter, up to 2.5 mm. and 30cm. from the tip, there 
is no marked change in the appearance of the chlorophyll apparatus of the 
stem, butin a branch 3.5 mm. in diameter and 40 cm. from the tip a marked 
modification is found. This is largely owing to the formation of cork. 
The phellogen arises in the parenchyma between the hard bast and the cam- 
dium and by its activities cuts the entire chlorophyll band off from the 
living portions of the stem. As an immediate consequence the chlorophyll 
band becomes at once a portion of the cork. Ina branch 2.5 mm. in diam- 
eter no chlorophyll was found in the wood or pith and none also in the 
most inner portion of the cortex. It was confined to a layer of cells, or to 
two layers, immediately beneath the phelloderm. 
The following measurements were made: 
- . Width of Depth of 
of branch. | from tip. | ‘cortex. |eMorophyll|chiorophyil 
mm. em. & K& B& 
1.5 5 240 67.2 25.6 
2 20 232.4 83.2 28.8 
2.5 30 249 60.8 32 
3-5 40 @ig |i; eases ||. eens 
