DESCRIPTION OF PLATES. 



Plate I. Stages in the development of Heterodera radicicola (Greef) Mull., etc. Figs. 

 1 and 2.— Eggs in two different stages of development, X 350. Fig. 3.— Larva 

 immediately after escaping from egg, X 105. Fig. 4.— Anterior portion of 

 same, X 410. Figs. 5 to 8. — Developmental stages of larvae before sexual differen- 

 tiation is apparent, X 105. Fig. 9.— Molt in which sexual differentiation first 

 becomes apparent, female nematodes approaching sexual maturity, X 105. 

 Fig. 10. — Sexually mature female nematode, a somewhat more advanced stage 

 than shown in figure 9, X 105. Fig. 11.— Posterior portion of sexually mature 

 female nematode somewhat compressed, X 220: a, Anal opening; 6, alimentary 

 canal; c, genital opening; d, vagina; e, c, uteri; /, /, ovaries. Fig. 12.— Egg- 

 bearing female nematode, X 47: a, Alimentary canal; h, loop of uterus; c, 

 genital opening. Fig. 13. — First visible stage in differentiation of the male 

 nematode (compare with fig. 9), X 105: t, t, Testis. Fig. 14.— Mature male still 

 within larval skin, X 85. Fig. 15.— Mature male, X 85. Fig. 16.— Anterior 

 portion of adult male, showing spear and peculiar structure for guiding its 

 movements, X 930. Fig. 17.— Larva entering root of clover, X 100. Fig. 18.— 

 Larva of Heterodera schachtii Schmidt just escaped from egg (compare fig. 3), 

 X 105. Fig. 19. — Anterior portion of same, X 435. 



Plate IL Fig. 1. — Root-knot on sugar beets grown at the Subtropical Laboratory, 

 Miami, Fla. 1907. Photographed by E. A. Bessey. Fig. 2.— Root-knot on 

 squash, from Beeville, Tex. 1904. Photographed by W. A. Orton. 



Plate III. Fig. 1.— Root-knot on carrot, from Morrison, 111. 1908. Photographed 

 by W. W. Gilbert. Fig. 2. — Root-knot on red clover grown in a pot of sterilized 

 soil inoculated with affected roots of Ipomoea syringaefolia, Subtropical Labora- 

 tory, Miami, Fla., 1908. Photographed by E. A. Bessey. 

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