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NortH Haven Sanp Prains 607 
for along time. There are curious strands of lamellated scleren- 
chyma-cells with narrow lumina running through the cortex near 
the periphery. None of the cells contain starch. 
Diameter of entire root, -9 mm. 
‘« largest vessel, 66 su. 
VIOLA SAGITTATA.— The xylem is surrounded by phloem, 
though very young roots show the diarch arrangement. Endo- 
dermis present, composed of small rather irregular thin-walled 
cells. Cortex is made up of larger cells which have thicker walls. 
A few of the cortical cells are filled with a dark-brown substance. 
Diameter of root, .6 mm. 
‘* —** central cylinder, -25 mm. 
‘« _ §* largest vessels, 23 UL. 
ONAGRA BIENNIS. — Real primary structure not found, but sec- 
tions of small roots show a number of large vessels in central 
portion surrounded by woody tissue. Around this is the phloem 
containing many large cells or vessels with raphides. On the 
outside of the phloem tissue are two distinct layers of phellogen, 
the cells being large, nearly uniform in size, and rectangular in 
Cross-section. These cork-cells have thin dark-colored walls and 
have developed from the pericycle, according to Strasburger (Lehr- 
buch der Botanik, ed. 5, 119), and have crowded and flattened 
the endodermal cells beyond recognition. These flattened endo- 
dermal cells may be found on the outside of the cork layer. In 
One section the cork-cells have not yet fully developed and the 
endodermal cells still remain. Several layers of cork-cells occur 
in older roots. Outside of the cork layer are several layers of 
much flattened cells which peel off in handling and are probably the 
bark. The cells have brown walls. 
LYsIMACHIA QUADRIFOLIA, — Several small vessels but no very 
large ones are found in the center of the root. The phloem 
patches are five in number and close to the endodermis, Endo- 
dermis is composed of cells that appear oval or oblong in cross- 
Section ; the walls are quite thick and are lamellated and pitted. 
The pericycle is made up of similar though slightly smaller cells. 
In the center of the root there is a group of sclerenchyma-cells 
with very thick walls which are lamellated and pitted. The corti- 
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