June 33 *x 933 
Disease Resistance to Onion Smudge 
1021 
Table l.—Lisi of onion varieties tested as to their susceptibility or resistance to smudge 
Color. 
1916 
1917 
1920 
1931 
White. 
White Globe. 
White Portugal. 
Queen. 
Mainmoth Silver Kmg. 
Extra Early Barletta. . 
Giant White Italian Tri¬ 
poli. 
White Globe. 
White Portugal. 
Queen. 
Giant White Italian 
Tripoli, 
White Globe. 
Crystal Wax Ber¬ 
muda. 
White Australian. 
White Portugal. 
Early White 
Queen. 
Yellow or 
brown. 
Southport Yellow Globe. 
Michigan Yellow Globe. 
Yellow Globe Danvers. 
Yellow Danvers. 
Yellow Strassburg. 
Prizetaker. 
Early Neapolitan Marzola. 
Australian Brown. 
Southport Yellow Globe. 
Michigan Yellow Globe. 
Yellow Globe Danvers. 
Yellow Strassburg. 
Yellow Globe. 
Ailsa Craig. 
Gigantic Gibraltar. 
Australian Brown. 
Red. 
Extra Early Red. 
Large Red Wethersfield. 
Southport Red Globe. 
Extra Early R^. 
Large Red Wethersfield. 
Red Globe. 
Extra Early Red. 
Red Bermuda. 
The inoculation studies were continu^ m moist ^ 
of spore suspension were placed directly upon marked ar^ of ^e sm- 
face thTs?ales. From certain of the bulbs the dry, outer scal^ w^e 
removed and the inoculum placed directly 
while in others the natural conditions were sunulated by placing me 
drops upon the dry scale. In no case did any infection whatever occur 
upon the dry outL scales of colored bulbs; and where the spores were 
eLmined i/the drops of inoculum no normal gemu^on 
In nearly all instances, however, inoculations m the same or si^l 
moist chLibers upon the succulent scales of bulbs from the 
source did take effect. The infected area was ch^actenzed first by a 
very rapid disappearance of the pigment, often within two days afte^e 
inoculations were made, followed by a gradual 
and underlying cells (PI. 2 , A). From all app^^ces “ 
vaded the so-called resistant varieties as aggressivdy ^ 
ceotible ones when the dry scales were removed. The outo scal(M, 
therefore, appear to serve as the b^er and to be responsible for the 
resistant property of the colored varieties. of 
ThrCapid destiuction of the coloring matter in succulent scales at 
first was very surprising in view of the marked toxicity of water extract 
5 pSeS scX which will be described later In fact, it necessi¬ 
tate^ further study of fungus invasion of the colored succulent scd^. 
Tfiis was done bv cutting tangential razor sections from the surface of 
the scale directly beneath the drop of inoculum so as to contain ti^ 
JstSbed eTdeLb with a few layers of the underlying cells. Ttoe 
sections were then examined in water mounts under the microscop . 
Bv this method the progress of the fungus could be watched from the 
instant of spore germination throughout the disappearance of the pip 
SS taS oi l red variety were used because it was much easier to 
follow the latter phenomenon in them than in those of the ye 
ties. It was fouSd that the process fSSiL 
that already described for white onion bulbs (24). After me tormation 
S the apwessorium and of the penetration tube, me mycelium developed 
&s?b«w^"cutide and sib-epidermal wall. Many cells were to be 
