172 BOTANICAL GAZETTE [MARCH 
The root 
The root stele at the point of attachment to the stem cylinder 
varies from diarch to pentarch; triarch and tetarch arrangements 
of the xylem are commonest. In passing from the base of the root 
toward the tip, the number of protoxylem points frequently 
increases by the splitting of one of the original protoxylem strands; 
in one case, the disappearance of a protoxylem strand was noted. 
In a few cases only, a hexarch arrangement was found; these roots 
were all very large. In general there is a definite relation between 
the size of the root and the number of protoxylem strands. 
Each phloem mass is a layer 1 or 2 cells in thickness, separated 
from the xylem by 3-5 layers of parenchyma. It is easily dis- 
tinguished by the somewhat thickened walls and the conspicuous 
“proteid granules” adhering to the walls. In the apical region of 
the root, the protophloem can usually be distinguished considerably 
in advance of the protoxylem. When a protoxylem strand splits, 
the phloem between the branches of the split strand connects with 
the phloem masses on either side. 
There is no pericyclic layer; the phloem abuts directly upon 
the endodermis (fig. ro), which can be readily distinguished by the 
suberized band upon the radial walls; it resembles the endodermis 
of Botrychium virginianum in all particulars. Two or three cells 
of parenchyma separate the protoxylem from the endodermis. 
Two general regions of the cortex about equal in thickness are 
distinguishable. In the inner region, the cell walls are heavily 
thickened by cellulose; simple circular or oval pits occur. In the 
outer region, the thickening of the cell walls is much less and gives 
the reactions of pectin compounds. Intercellular spaces of con- 
siderable size occur in the inner region; in the outer region, these 
are much smaller and become filled by the substance which con- 
stitutes the thickening of the cell walls. The endophytic fungus 
which occurs commonly in the roots is confined to the outer 
region, ; 
The outer walls of the surface cells are remarkably thickened, 
as shown in fig. 2. The thickening material is not cellulose, but 
gives the reaction of pectin compounds. The thickening may COn- 
tinue until the lumen of the cell is almost filled; even in these con- 
