276 
Journal of Agricultural Research 
Vol. XXXI, No. 3 
Allium nevadense in the far West, no American Allium is known to be 
susceptible, so far as the writer is aware. If it were found that some 
one of our New England Alliums is subject to this disease, then an 
explanation of its origin would be easy. 
(2) It would help settle the question of a possible relationship 
between Urocystis cepulae and some of the other species of Urocystis 
which occur on other species of Allium. 
(3) In a genus as large as Allium, it is probable that there are some 
resistant species which may be crossed with A. cepa and that from 
the hybrid progeny of which a desirable smut-resistant onion might 
be developed. The initial step is to determine how resistant the 
different species are, if they are resistant at all. 
EXPERIMENTS WITH ONION VARIETIES 
From the catalogues of American seed houses, 25 onion varieties 
which seemed to be distinct were selected. Seed of 29 European 
varieties were obtained from H. Zillig, of the Biologische Reichsan- 
stalt fur Land-und Forstwirtschaft, at Trier, Germany, who also 
was investigating the same phase of onion smut and who kindly sent 
seed of each of the varieties which he was trying. Three hundred 
seeds of each of the 54 varieties thus obtained were planted April 
25, 1924, in soil which was known to be very heavily infested with 
smut. When the seedlings came up there was seen to be considerable 
variation in the percentage of germination. Smut had appeared on 
all of the varieties after three weeks. All plants, irrespective of 
infection, were counted on May 30 to determine the percentage of 
germination, and at that time smut infection was estimated at about 
75 per cent on all varieties and none offered evidence of being strik¬ 
ingly more resistant than others. The smutted ones had already 
begun to die and continued to drop off throughout the summer. On 
August 11, all the remaining plants were pulled and counted, and 
the percentage of infection was determined by comparing the number 
of healthy plants at that time with the number which had germinated 
on May 30. 
The results are presented in Table I. They do not indicate that 
there is any important degree of resistance in any of the 54 varieties 
tried. Neither does the theory of some onion growers, that the red 
varieties are more resistant, find any support in these results. The 
pigmentation factor shows no relation to the resistance factor. 
There are, however, still other varieties which have not been tested, 
and it is possible that some more resistant variety may be found 
among them. It is therefore important that this line of work should 
be continued. 
