598 BRITTON: VEGETATION OF THE 
radially outside of the vessels. Between and around the vessels 
and phloem patches, and in the center of the root, the tissue is 
made up of rather thick-walled parenchyma-cells with small inter- 
cellular spaces. Endodermis is composed of rather thin-walled 
cells of medium size. Cortex is made up of thin-walled cells 
mostly tearing off in cutting. 
Diameter of central cylinder, .29mm. 
ss ** ‘Jargest vessels, 40 pt 
PANICUM UNCIPHYLLUM.* — The sections examined show sev- 
eral large vessels in the root between and around which are rather 
thick-walled parenchyma-cells. Phloem patches are small and 
numerous, arranged ina circle around the vessels, which is the 
usual arrangement in grasses. The endodermis is well developed 
and is composed of large cells rectangular in transverse section ; 
cell-walls are of medium thickness, and there are a few small inter- 
cellular spaces between the endodermis and the central tissue. 
There is no well-developed pericycle. The cortex is made up of 
large cells with very thin undulating walls. In one or two layers 
next to the endodermis the cells are rectangular in cross-section, 
but the other cortical cells are very irregular. Some of the cells 
in the central cylinder are filled with starch-granules. 
Diameter of root, .35 mm. 
‘* _** central cylinder, .20 mm. 
«© ** Jargest vessels, 27 # 
ANDROPOGON scopaRIUs.—In the specimens examined there 
are thirteen vessels arranged in a circle half-way from the center 
to the periphery of the root and separated by rather thick-walled 
parenchyma-cells. Just outside the row of vessels are very small 
patches of phloem, hard to make out except by the thin cell-walls. 
Between these areas and the endodermis the cells are mostly 
empty, with rather thick pitted walls. A few cells contain starch- 
granules and some appear to be sieve-tubes. Endodermis prom 
inent ; cells rectangular in cross-section, walls thin on the out-. 
side but thickened peculiarly on the inside and showing lamellae 
and pits. Cortex consists of three or four layers of thin-wal 
cells rectangular in transverse section, mostly tearing off in cuttilé: 
* See Rhodora, 3: 121, 190%. 
alled 
