346 CHURCH: THE BULB IN COOPERIA DRUMMONDII 
of the cotyledonary sheath. The bulge shown (Fic. 14) is due to 
a young root. This first adventitious root, 7, originates (Fic. 8) 
at the node of the second foliar leaf and, growing downward, cuts 
its way through the first leaf and the cotylar sheath. A slightly 
older root with a well differentiated root cap and primary 
tissues (dermatogen, periblem, and pleurome) is shown in Fic. 
18. This seedling is from the same planting as that of Fic. 
8. The young root arising endogenously in the bulb- or stem-axis 
will, together with similar companions, replace the tap or primary 
root. The primary root is still active at this time. The secondary 
roots, which become functionally the principal roots of Cooperia 
Drummondti, are adventitious roots, derived from an active 
cambium tissue below and to one side of the growing point. They 
force their way through the tissue of the bulb-axis and form at 
first roots to one side of the early dying primary root and later a 
complete ring of such roots. The roots of Cooperia Drummondii 
have root hairs. The vascular bundles which develop in the 
secondary roots anastomose with the bundles already formed in 
the stem-axis. The complete working out of the origin and 
arrangement of the vascular traces in the stem-axis of Cooperia 
Drummondti would be very difficult, so complicated is the anasto- 
mosis. Both the primary root and the secondary roots show a 
wrinkling on their surface which is connected with the drawing 
down of the bulb into the soil by contraction of said roots. A bulb 
may be drawn down in this fashion to a depth of over seven inches. 
The puckered or wrinkled condition of the primary roots 
(Fics. 8, 15, 17 and 18) is due to contraction of at least some of the 
tissues. This phenomenon occurs in the adventitious roots also. 
Its hypothetical mechanics will be discussed later. The outlay of 
root tissue in FIG. 17 has a narrow slice marked off. This slice 
has been divided into three sections—1, 2 and 3. If this narrow 
strip of root is studied with the high power of the microscope we 
have under observation cellular tissues similar to those of FI. - 
19, where I represents the vascular region; 2, the parenchyma; 
and 3, the cork and other dead tissues. Evidently the root con- 
traction has entirely damaged only the outer cells, which are now 
dead tissue. The inner cells have in some way accommddated 
themselves in part to the strain. The trace is still intact although 
