FIG. I A-D. Non-infected and infected roots of wheat, showing the early stages of infection by second-stage larvae of M. naasi. A. Transverse section of a non-infected root, 20 days after germination (X 105); B. Intracellular larvel migration in the cortex, I day after inoculation (X 105); C. Transverse section showing 31 larvae (Nem) embedded in the cortex 2 days after inoculation. Note the disruption of adjacent cortical cells (× 105). D. Nematode with its lips in the pericycle region, 3 days after inoculation (X 375)