68 Transactions British Mycological Soctety. 
show the same germinal hyphae three days and thirteen days 
respectively after germination indicates that budding may occur 
whilst the sporidia are still attached to the hyphae. The con- 
ditions determining the budding of the sporidia are as yet 
obscure though one factor is certainly the presence of nutriment 
in a concentrated form. fos: 
It appears probable that budding or yeast formation is 
abnormal, and may not take place under natural conditions. 
Conjugation of sporidia has not been observed. 
Germination of Sporidium. The germination of sporidia in 
water has not been seen, but in onion juice one or rarely two 
polar germinal tubes were produced which ceased to grow after 
reaching a length of about 15 p. 
INFECTION OF HosT PLANT. 
It is now firmly established that only seedlings are susceptible 
to attack; transplants and setts not being affected (s). Thaxter 
showed that infection is wholly subterranean ; a statement which 
has been repeatedly confirmed by the writer. It is difficult, 
however, to determine the point at which infection takes place 
since primary infection and sporulation cannot be demonstrated 
in the same specimen owing to the early death of the vegetative 
mycelium. Pot cultures of onions grown in soil contaminated 
with onion smut showed sporulation invariably within 2 mm. 
of the collar (i.e. junction of root and cotyledon) and frequently 
in the collar itself. This observation strongly suggests the collar 
region as the one at which infection normally takes place. The 
probability that this is correct is increased by the fact that 
hyphae indistinguishable from those of Urocystis cepulae could 
be demonstrated in the root hairs in the collars of very young 
seedlings grown in smutted soil. 
Thaxter suggests that since spore masses may occur at the 
leaf tip infection may be possible also through the cotyledon 
before appearing above ground. Whilst this is, of course, 
possible, there is no experimental evidence in support of this 
view and it should be pointed out that the sporogenous hyphae 
frequently produce spore masses at intervals in the cotyledon, 
so that, externally, the dark patches appear to be separated by 
healthy tissue. It may well be, therefore, that sporulation at 
the leaf tip is only an extreme case of this discontinuous spore 
formation. 
Method of Infection. The exact method of infection, i.e. 
whether sporidial or by direct penetration of the promycelium 
does not appear to have been satisfactorily demonstrated for 
any species of Urocystis, though Plowright (6) states that he 
successfully inoculated the leaf of Ranunculus repens with the 
