418 HETERODERA RADIO I COLA. 



Orton, W. A. : "The Wilt Disease of the Cowpea and its Control." 



Bull, 17; pt. 1. Bureau of Plant Industries, U.S. Dept. Agric. 



1902. 

 Rolfs, P. H.: "Diseases of the Tomato." Bull. 47. Florida 



Agric. Expt. Stn. September, 1898. 

 Stone, G. E. and Smith, R. E. : "Nematode Worms." Bull. 55, 



Hatch Expt. Stn. of Mass. Agric. Coll. November, 1898. 

 Scofield, C. S. : "The Nematode Gall Worm on Potatoes and 



other Crop Plants in Nevada." Circ. 91, Bureau of Plant. 

 [ndustr., U.S. Dept. Agric. Issued February, 1912. 



Explanation' of Plates VI-VIII. 



All figures were drawn by the author with a camera lucida 

 and Zeiss drawing table. 



Explanation of Letters used in Figures. 

 An. — Anus. 

 Ct. — Cuticular stria;. 

 Exc. Pr. — Excretory Pore. 

 Int. — Intestine. 



Oes. comm. — Oesophageal nerve commissure. 

 Oes. — Oesophagus. 

 Oes. bib. — Oesophageal bulb. 

 Ov. rud. — Rudiments of Ovary. 

 Rect . — Rectum . 



Cap. spic. — Copulatorv spicules. 

 Testis. — Testis. 

 VI v. —Vulva. 



Plate VI. 



Figs. 1 — 10: Eggs of Heterodera from potato in different stages 



of development, x 250. 

 Fig. 11 : Embryo just prior to hatching, x 250. 

 Fig. 12: The free-living larva, x 250. 

 Fig. 13: The parasitic larva just commencing to swell, x 250. 



Plate VII. 



Fig. 14 : Parasitic larva at commencement of sexual differen- 

 tiation, x 250 



Fig. 15 : Immature female still within larval skin, x 250. 



Fig. 16: Mature female after casting larval skin. Ovary showing 

 and external orifices of vulva and anus visible, x 200. 



Fig. 17: Mature gravid female containing eggs, x 95. 



Plate VIII. 



Fig. 18: Fully formed male still encased in larval skin, x 150. 

 Fig. 19: Free mature male. (This specimen shows the double 

 nature of the testis), x 150. 



