604 BRITTON: VEGETATION OF THE 
CYPRIPEDIUM ACAULE, — Root has radially arranged bundle 
with eight xylem points, and no very large vessels. Endodermis 
present, of thick-walled cells which are interrupted opposite the 
radiating points of xylem, and replaced by thin-walled cells. The 
cortex is made up of very large, circular, parenchyma-cells with 
thin walls, and intercellular spaces. Some of the cells contain small 
quantities of starch. The two outside layers contain smaller cells 
which are rectangular in cross-section. 
Diameter of root, about 2.00 mm. 
fs ‘* central cylinder, .45 mm. 
ti ** cells of cortex, .13 mm. 
= ‘* largest vessels, 30 4 
_ Potyconum Convotvutus. — Primary structure not found in 
the material examined, but the secondarily thickened root is re- 
markable for the size of the vessels, some of which are from one 
sixth to one seventh the diameter of the root. There are no large 
parenchyma-cells in the cortex, but several strands of thick-walled 
cells run through the cortex near the periphery. The transverse 
section of a secondarily thickened root is shown on fi. 28, ¢ 
Roots examined were somewhat flattened. 
Diameter of root, .83 x 1.0 mm. 
Ms ** largest vessels, 106 x 166 uv 
FraGaria Virciniana. — Central cylinder is rather small and 
xylem elements appear triangular in cross-section, and sur 
rounded by the phloem. Endodermis is distinct, being made up 
of small cells, with walls of medium thickness, filled with starch- 
granules, Central cylinder is surrounded by much parenchyma- 
tous tissue of large thin-walled cells mostly circular in cross 
section. Cortex separates in cutting, and is made up of circular 
cells a trifle smaller than the parenchyma-cells and with thicker 
walls. Certain cells of the cortex, parenchyma and central por 
tion contain brown granules; such cells are also found between 
the xylem vessels, and several cells near the endodermis contain 4 
brown or yellow substance resembling resin. Abundance of 
parenchymatous tissue must be of considerable use in storing 
water. 
Diameter of root, 1,00 mm. 
a ** central cylinder, .25 mm. 
Ms ‘* largest vessels, 27 bt 
