DEPARTMENT OF AGRICULTURE


i), which will break the eggshell and become free in the soil by the
cracking of the root or at the time of its decay. The egg stage is un-
questionably the most resistant, and it is in this stage that the nematode
may survive long periods of adverse conditions. A larva free in the soil
succumbs quickly to adverse conditions such as lack of moisture, exces-
sive heat, direct sunlight, or cold. Males develop under certain condi-
tions and are slender, eel-like organisms of very different shape from
the females (Fig. 12 E and F). Their development is very interesting;
instead of growing to a pear shape like the females, a male larva at the
sausage-shaped stage is transformed into a threadlike, cylindrical nema-


r


 Figure 16.-Photomicrograph of two adult female root-knot nematodes in a
balsam plant root (Impatiens balsamina); the giant or nectarial cells are seen as
darkened cell masses in the axial cylinder of the root; the jelly mass secreted by the
females is seen surrounding the broad posterior end of the females, the pointed head
end of which is embedded in (upper specimen) or directed toward (lower specimen)
the giant or nectarial cells. x 135


1" I