528 Wisconsin Academy of Sciences , Arts , and Letters. 
barley caused only a slight infection (“subinfection”) on H. 
bulbosum and H. maritimum; (3) that conidia from barley 
did not infect H. jubatum, II. sylvaticum, H. murinum and 
II. secalinum. 
He explains the infection of H. bulbosum and II. maritimum 
as due to the fact that many conidia were sown at one place 
upon the leaves, and when these germinated a great number of 
haustoria attacked each of the epidermal cells in that region. 
This is supposed to have had the result that the enzyme as¬ 
sumed to inhibit the growth of the barley mildew on these 
plants was incapable of preventing the growth of so many haus¬ 
toria, and thus some secured a foothold and a mycelium was 
formed which was able to develop and produce a few conidi- 
ophores with conidia. 
In his experiments with H. secalinum, H. murinum and H. 
sylvaticum J noi immediate infection followed inoculation. A 
few weeks later, however, several of the plants were found in¬ 
fected. As these plants were kept in a hot, ill-ventilated room, 
Salmon concludes that their vitality was lowered to such an ex¬ 
tent that they could no longer resist the attack of the mildew 
of II. vulgare which was abundant around them. 
It has further been found that the Oidium on Euonymus 
japonicus is also limited in its capacity for infecting species of 
this genus, some species being infected while others are not. It 
is not known to what species of mildew this conidial stage be¬ 
longs. Arcangeli (1, 2) has determined the fungus as the conid¬ 
ial stage of Sphaerotheca pannosa (Wallr.) Lev. Salmon (31), 
however, thinks the fungus is the conidial stage of some species 
of Erysiphe or Microspha&ra. As a result of infection ex¬ 
periments, Salmon has found that the Oidium on Euonymus 
japonicus will infect E. japonicus var. aureus, var. ovatus au¬ 
reus, var. microphyllus, var. albo-marginatus, var. President 
Gunter, E. radicans var. microphyllus, var. Silver Gem, but not 
E. radicans var. carrierei , E. nanus, E. europaeus, E. chinensis, 
E. americanus var. angustifolius, Oelastrus scandens, 0. articw- 
lotus, C. orixa , and Prunus laurocerasus var. latifolia. With 
two exceptions, the negative results rest upon only one experi- 
