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 Figure 13.-Photomicrographs of developing larvae of a root-knot nematode in
roots of balsam (Impatiens balsamina L.) A. Swollen portion of a root with numer-
aus larval nematodes arranged around its axial cylinder ( X 25); B. single young
larva, its body only slightly swollen but the root tissue cells around its head end
already enlarged to form the so-called giant or nectarial cells. The immigrating root-
knot nematode larva in settling down for its permanent, life-long location injects
secretions of its oesophageal glands into the root tissue. These injections stimulate
the cells to increased growth and, by secretion, to the production of a type of fluid
Food which is directly assimilable by the nematode. It appears that this food ma-
terial is of such comparatively simple structure that a regular digestion in the
intestine of the parasite is not further necessary. The intestine of these parasites
appears to be mainly a storage organ for food reserves and the rectum and anus
are often vestigial (x 63); C. same as B but a later stage (x 100); D. same as
B and C but still a more advanced stage than C. The molt of the larva is seen as
 faint mark surrounding its body (x 100).