30 BULLETIN 842, U. S. DEPARTMENT OF AGRICULTURE. 
In examining many of the common grasses, especially Bromus 
secaZinus and Dactylis glomerate, growing in and near severely dis- 
eased fields of wheat in Virginia, the writer has been unable to find 
nematode galls of either the flower or leaf. The evidence at hand, 
therefore, seems to indicate that the nematode on wheat is not iden- 
tical with forms producing flower galls on wild grasses. 
Not infrequently nematode galls located only on the leaves of 
grasses have been reported. Some of these are caused by organisms 
morphologically similar to and by some investigators also thought to 
be identical with Tylenchus tritici. The writer has found such leaf 
infections particularly abundant on Calamagrostis canadensis in 
Wisconsin, but these are caused by a species of Tylenchus different 
morphologically from the wheat nematode. In general appearance 
they resemble somewhat the uredinia of certain rusts, for which 
they have been mistaken. As a rule, they are small, yellow, ellip- 
soid swellings, about 5 mm. long. '2 mm. wide, and 2 mm. thick, which 
involve the entire thickness of the leaf at the affected point, causing 
it to protrude slightly from the upper and lower surfaces. Their 
long axis extends in a direction parallel to the midrib, and they may 
occur on any portion of the leaf. Grasses so affected have been ob- 
served many times in both America and Europe. As in the case of 
the nematodes causing flower galls on various grasses, it is not pos- 
sible, on account of the brevity of descriptions, to determine posi- 
tively whether all the nematodes in the leaf galls of grasses differ 
from Tylenchus tritici. On the whole., it seems rather unlikely that 
any of them are identical with the wheat organism, since the latter 
is primarily a parasite of the inflorescence and only occasionally pro- 
duces leaf galls. 
An interesting and important question is whether identical or- 
ganisms are responsible for the leaf and the flower galls of the wild 
grasses, on some of which both types of attack occur. In the case 
of wheat, the writer has shown that the two kinds of galls may be 
induced by Tylenchus tritici. Davaine (11) obtained similar results 
and Kieffer (20) also noted definite leaf swellings which contained a 
species of Tylenchus very likely identical with T. tritici. but Marci- 
nowski (22) was unable to find leaf galls on wheat. 
From what has been said it is evident that considerable investiga- 
tion is needed to extend our knowledge of the relation between 
Tylenchus tritici and other nematode- occurring on grasses 
METHODS OF SPREADING THE PARASITES. 
Only in its second larval stage does the parasite constitute a source 
of new infection. All other stages of the life cycle are more or less 
transitory, unable to withstand unfavorable conditions, and unable 
to live or develop for any appreciable time outside the host plant. 
