600 BRITTON: VEGETATION OF THE 
SPOROBOLUS VAGINAEFLORUS. — Small root has two large ves- 
sels and several much smaller ones. Endodermis prominent, of 
cells with inner walls strongly thickened showing lamellae and 
pits. Pericycle of thick-walled cells. Cortex made up of one or 
two layers of rather irregular large cells with walls of medium 
thickness and brown color. 
Diameter of central cylinder, .I mm. 
Small root. 
00 ‘¢  ** largest vessel, 20 # 
In larger roots there are four large vessels and two or three 
small ones. Some roots have three large vessels. Endodermis 
has cells with inner walls much less thickened than in small root, 
though lamellae and pits are still prominent. Cortex composed 
of about five layers of cells, the outer layers having thicker walls 
than the inner layers. No starch. Cross-sections of both large 
and small roots are figured on f/. 27, 6 and c. 
Diameter of entire root, .25 mm, 
Large root. | «¢ «© central cylinder, .18 mm. 
+4 ‘* largest vessels, 37 bh 
Poa compressa. — Young root has a single vessel in the cen- 
ter with rather thick-walled cells between this and the endodermis. 
The endodermis is composed of thick-walled lamellated cells. Out- 
side and next to the endodermis is a layer of cells quite different 
from the endodermal cells and those of the cortex. These cells 
are oblong in transverse section, have thicker walls than the cor- 
tical cells, and of the same color as the endodermal cells. Cells 
of the cortex have thin walls, and are irregular in shape. 
Diameter of root, .25 mm. 
«¢ © central cylinder, .I mm. 
ee ee OBR 17 ub 
Rhizome: central portion is made up of large empty pith- 
cells with large intercellular spaces. This tissue is surrounded 
by a layer of sclerenchymatous tissue several cells in thickness 
with which all of the bundles are connected; some of the bun- 
dles are entirely surrounded by it, but most of them and espe- 
cially the larger bundles are just inside this ring of sclerenchym4- 
Outside are small empty parenchyma-cells with thin walls an 
