Mar. 34, 1933 
Downey Mildew on Lettuce in California 
993 
the development of the New York. The latter is so well established in 
the trade that an advocacy of substitution by Iceberg would be viewed 
askance by shippers at present. On account of an unfolding of its 
advantages in the summer months, when a small amount of Iceberg is 
shipped, the two varieties rarely meet on the market in competition* 
The variety known as Hanson, an intermediate variety between New 
York and Iceberg, shows considerable resistance to downy mildew. The 
solution of the problem rests in the selection of individuals among the 
resistant varieties, for firmness and size of head. 
SUMMARY 
Climatic conditions in California are favorable and conducive to the 
growth of Bremia lactucae on lettuce in the field. The abundance of 
file fungus has given rise to an important problem in transportation as 
well as in the field. Reports by inspectors of the Bureau of Markets 
point to frequent deterioration of lettuce in transit due to this fungus, 
which invades the plant in the field. 
The solution of the field problem has been approached in a large 
measure by the determination of the existence of resistance in certain 
varieties of lettuce. 
The additional method of reproduction found in Bremia lactucae on 
lettuce in California in the form of zoospore production, heretofore unre¬ 
corded, does not change the position of the fungus in the Peronospo- 
raceae. 
LITERATURE CITED 
(1) Arthur, J. C. 
1886. LETTUCE MILDEW. PERONOSPORA GANGUFORMS DEB. In N. Y. State 
Agr. Exp. Sta., 4th Ann. Rpt., 1885, p. 279-280, fig. 4. 
(2) Bary, Anton de. 
1863. RECHERCHES SUR LE D^VELOPPEMENT DE QUELQUES CHAMPIGNONS PARA¬ 
SITES. In Ann. Sci. Nat. Bot., ser. 4, tome 20, p. 5-143, 13 pL 
Bibliographical footnotes. 
(3) Berkeley, M. J. 
1846. OBSERVATIONS, BOTANICAL AND PHYSIOLOGICAL ON THE POTATO MURRAIN. 
In Jour. Hort. Soc. London, v. 1, p. 9-34, 4 pi. 
(4) Burrill, T. J. 
1876. upon parasitic fungi. In Ill. Mus. Nat. Hist. Bui. 1, p. 52-59. 
(5) Farlow, W. G. 
1883. enumeration of the peronosporeae of the united states. In 
Bot. Gaz., V. 8, p. 305-315. 
(6) Halsted, Byron D. 
1882. fungi injurious to vegetation with remedies. In 15th Ann. Rpt. 
Cbnn. Bd. Agr., 1881-82, p. 157-191. Discussion, p. 177-191. 
(7) Marchal, E. 
1902. DE L'IMMUNISATION DE LA LAITUE CONTRE LE MEUNIER. In Compt. 
Rend. Acad. Sci. [Paris], tome 135, p. 1067-1068. 
(8 ) Saccardo, P. A. 
1888. sylloge fungorum. v. 7. Patavii. 
(9) Tracy, W. W., Jr. 
1904. American varieties of lettuce. U. S. Dept. Agr. Bur. Plant Indus. 
Bui. 69, 103 p., 27 pi. 
