NortH Haven SAnpD PLAINS 605 
POTENTILLA CANADENSIS. — Primary structure shows three 
vessels in the bundle surrounded by thin-walled cells —the 
phloem. Endodermis is composed of large cells nearly circular 
in cross-section, with dark walls of medium thickness. Pericycle 
of smaller cells with light-colored walls. The bundle begins as a 
diarch. The cortical cells are very large and irregular in shape 
with thin undulating walls. Older root shows three-pointed xylem 
with alternating phloem patches. No endodermis immediately 
surrounds the bundle, but near the periphery of the section is a 
layer of small rectangular cells greatly resembling an endodermis. 
These cells are closely packed with starch. Between this layer 
and the xylem of the bundle the tissue consists of rather thick- 
walled parenchyma-cells, most of which appear empty, but a few 
are densely packed with granules. 
Diameter of root, .18 mm. 
ss 6 central cylinder, I mm. 
“¢ ‘* largest vessels, ¥3 py. 
CROTALARIA SAGITTALIS. — Primary structure not observed. 
Roots in which secondary thickening has taken place have from 
twenty-five to thirty large vessels arranged irregularly. Strands of 
thick-walled sclerenchyma-cells run through the cortex near the 
periphery and some similar cells occur in the central cylinder. 
Resembles Cassia very closely in structure, but the sclerenchyma- 
tous tissue is more abundant than in Cassia. Shown on fi. 28, d. 
Diameter of root (thickened), .I mm. 
‘ -« central cylinder, .5 mm. 
‘«  “ Jargest vessels, 46 p. 
Lupinus PERENNIS. — Central cylinder of the root is oval in 
cross-section, and small for the size of the root. Xylem has the 
diarch arrangement whith phloem on both sides. Sclerenchyma 
Strands appear in connection with the phloem tissue. Endodermis 
is apparent, though the cells are rather irregular and have thin 
walls. Outside the endodermis the root is made up of very large 
thin-walled parenchyma-cells, the largest cells having a diameter 
of 504. Cortex consists of a single layer of small thin-walled 
cells with small brown granules. 
