125 
showed browning and incipient rot of the basal portion of the stem. Micro- 
scopic examination and agar platings from these stems gave results identical 
with those stated above. One plant that was so badly rotted in the pot 
as to fall over was found bearing Helminthosporium conidia on its surface. 
Conidia produced in Moist-chamber Culture 
While stems with diseased lesions, either from the field or greenhouse, 
when placed in an ordinary moist-chamber rarely gave Helminthosporium 
conidia (or, if they did, only in small numbers), if the diseased stems were 
placed on wet filter-paper in moist chamber and rather closely covered 
with wet filter-paper Helminthosporium conidia invariably developed in 
quantity on the lesions, the fungus eventually spreading throughout the 
available wheat-tissue and producing conidia over the whole surface 
(cf. with page 95). 
Evidence from Inoculation 
Severed, live wheat-shoots, grown under aseptic conditions, were placed 
as under standard conditions (Appendix, page 180), except that the shoots 
were not autoclaved but put, living, upon the inoculated agar. All such 
shoots rotted rapidly and completely, the shoot being eventually covered 
by Helminthosporium conidia. Since direct examination showed no 
contamination, it is evident that H. No. 1 can cause rot of the wheat tissue. 
To determine the relative rotting power of this organism and other 
Helminthosporiums under these conditions, fresh aseptic shoots of corn, 
wheat, oats, barley, and rye were laid on washed agar with the growing 
tip toward the circumference of the dish, and the cut end in contact with 
the outer edge of the spreading mycelium of a colony about 5 cm. in diam- 
eter. These were examined after 2 days and again after 5 days, and the 
rate of browning was carefully calculated. In this way seventeen strains of 
Helminthosporium were tested as to their ability to produce rot in live, 
severed cereal-shoots. H. No. 1, the foot-rot organism, showed high 
rotting ability, completely rotting a wheat shoot 11 mm. long in 5 days, 
while H. No. 2 (H. ravenelii) produced no rot on any cereal. H. No. 1 
rotted corn also, but much less rapidly than it did wheat, and its rate 
on oats, barley, and rye was still less. Several other numbers showed 
strong rotting power on wheat shoots, notably H. No. 10 (labeled H. 
teres), isolated by Dr. Stakman from barley, H. No. 9 isolated by him 
from wheat, and H. No. 13 (labeled H. sativum), isolated by Dr. Durrell 
from barley. 
