1038 
Journal of A gricuUural Research voi. xxiv, No. la 
(4) The expressed juice of succulent onion scales is highly toxic to 
the fungus; this effect is seemingly due in large measure to the volatile 
onion oil. The extracts from resistant and from susceptible varieties 
have essentially equal degrees of toxicity. The onion oil apparently is 
not a factor contributing to varietal resistance to smudge in the northern 
Globe types, but its importance in limiting the parasitic action of the 
fungus is suggested. 
(5) The red and yellow colors in onion bulbs are due to pigments which 
are present in the cell sap of the outer epidermal layer. This color is 
most intense in the dry outer scales, and at least a portion of the pigment 
in these is readily soluble in water. 
(6) Water extract of dry outer pigmented scales causes abnormal 
germination and retards growth of the fungus, while that from dry outer 
white scales does not. Essentially the same reaction was recorded with 
the yellow as with the red scales. 
(7) A substance (or substances) present in the dry outer scales of 
resistant bulbs and closely associated or identical with the red and yellow 
pigments is apparently the chief factor causing resistance to smudge. 
Studies are now being directed toward isolation and identification of fiie 
toxic entity. 
(8) Within the range determined for host tissue, variation in the 
hydrogen-ion concentration of onion decoction as a medium affects 
neither germination nor growth of the fungus. 
LITERATURE CITED 
(1) Berkeley, M. J. 
1851. [a new onion disease.] In Card. Chron., 1851, no. 38, p. 595, 2 fig. 
(2) Bernard, Noel. 
1911. SUR LA roNCTioN FUNGICIDE DEs BULBES d’ophryd^es. In Ann. Sci. 
Nat. Bot., ser. 9, t. 14, p. 221--234, 3 fig. 
(3) Comes, Orazio. 
1913. DELLA RESISTENZA DEI FRUMENTI ALLE RUGGINI STATO ATTUALE DELLA 
QinsTiONE E PROVVEDiMENTi. In Atti. R. 1 st. Incorrag. Napoli, 
ser. 6, V. 64, p. 419-441. Letteratura e note, p. 437-440. 
(4) — 
1914. DELLA RESISTENZA DEl FRUMENTI ALLE RUGGINI, ED IN GENERALE 
DELLE PIANTE ALLE LORO CAUSE NEMICHE. In Aim. R. Scuola. Sup. 
Agr. Portici, ser. 2, v. 12, p. 419-473. Bibliographical footnotes. 
(5) Cook, Melville Thurston, and Wilson, Guy West. 
1915. THE INFLUENCE OF THE TANNIN CONTENT OF THE HOST PLANT ON ENDO- 
TmA PARASITICA AND RELATED SPECIES. In Bot. Gaz., V. 6o, p. 
346-361. 
(6) FrommE, F. D., and Wingard, S. A. 
1921. varietal susceptibility of beans to rust. In Jour. Agr. Research, 
V. 21, p. 385-404, pi. 69-73, Literature cited, p. 404. 
(7) Gildemeister, Eduard, and Hoffmann, Friedrich. 
1913. TfeE VOLATILE OILS. Ed. 2. Translation by Edward Kremers. v. i. 
677?., 74 fig. New York. Bibliographical footnotes. 
(8) Halsted, Byron D. 
1891. REPORT OF THE BOTANICAL DEPARTMENT. In N. J. Agr. Exp. Sta. 
nth Ann. Rpt., 1890, p, 323 “ 453 > 6 fig., 24 pi. 
(9) Hawkins, L. A., and Harvey, Rodney B. 
1919. PHYSIOLOGICAL STUDY OF THE PARASITISM OF PYTHIUM DEBARYANUM 
HESSE ON THE POTATO TUBER. In JouT. Agr. Research, v. 18, p. 
275-298, 2 fig., pi. 35-37. Literature cited, p. 295-297. 
(10) Jones, L. R., Giddings, N. J., and Lutman, B. F. 
1912. investigations of the potato fungus phytophthora infestans. 
U. S. Dept. Agr. Bur. Plant Indus. Bui. 245, 100 p., 10 fig., 10 pi. 
(partly col.) Literature, p. 88-93. 
