EPHEDRA ANTISYPHILITICA. 15 
is, of course, without chlorophyll. However, at this time, in addition to 
segments of the original chlorophyll band, there extends beneath the cork at 
least one layer of cells which are chlorophyllaceous. It does not appear 
that the phelloderm contributes to the chlorophyll apparatus. From these 
circumstances it happens that stems which appear brown or gray in color and 
give no visible indication of chlorophyll are, however, chlorophyllaceous. 
With the further development of the bark the primary cortex, except the 
single layer of cells which contain chlorophyll and which lie immediately 
within the phellogen, is entirely cut off, and with this process the most 
considerable portion of the chlorenchyma of the stem disappears. When 
chlorophyll quite left the stem was not learned. Inastem 7.5 mm. in 
diameter, in which no trace of the primary cortex remained, chlorophyll 
was to be seen in the outer medullary rays of the woody cylinder, in the 
rays of the cortex, and sparingly in parenchyma connecting the ends of the 
latter. Stems 1.1 and 1.5 cm. in diameter give no trace of chlorophyll in 
either wood or pith. 
FOUQUIERIA SPLENDENS. (Fig. 6.) 
Fouquieria occurs on dry, well-drained slopes. The plant used in this 
study is growing on Tumamoc Hill not far below the Laboratory. 
The young stem, 5 mm. in diameter, is characterized by three well- 
defined areas, namely, (1) an external shell of sclerenchyma, within which 
is (2) parenchyma containing chlorophyll, and within this is (3) the inner 
cortex, wood, and pith. The relative extent of the three divisions will be 
apparent from the sketches. The external shell is part of the primary 
cortex and is morphologically the base of the spines of the stem, which in 
turn are morphologically midribs of the primary leaves. The cells of the 
external shell early take on the characteristic thickening and turn brown, 
and in stems 5 mm. in diameter the shell forms a continuous covering. 
When the stem increases in diameter, however, the mass of sclerenchyma 
connected with each spine draws away from the mass connected with every 
other spine, and the intervening space is occupied by a waxy tissue which 
is somewhat greenish. The area covered by these two classes of tissue 
is more and more disproportionate in amount as the stem grows until in 
the oldest parts the surface is practically all covered by the newer tissue. 
The chlorophyll is confined to the parenchyma, which lies immediately 
within the shell of sclerenchyma or the newer tissue that succeeds it. It 
is composed wholly of cuboid, thin-walled cells with prominent intercellular 
spaces. 
So far as I have observed, chlorophyll is always present in the stems of 
Fouquieria, of whatever size. In stems 5 mm. in diameter the chlorophyll 
band forms a continuous ring in the outer portion of the cortex. As the 
shell base of each spine becomes separated from the base of the other con- 
tiguous spines in the manner above described, breaks occur in the chloro- 
