PLANT NEMATODES THE GROWER SHOULD KNOW 37


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 Figure 25.-Drawing of a spiral nematode (Helicotylenchus sp.) attacking a
rootlet of sweet clover (Melilotus sp.) The anterior end of the nematode has
deeply penetrated the root tissues; dotted region indicates the extent of cell necrosis
evidenced by discoloration; specimen collected by F. R. Jones, Madison, Wis.;
x 333.