128 
the cortical tissue was seen to be crowded with Helminthosporium myceli- 
um coursing mainly in the longitudinal direction of the root. The mycelial 
threads within the root cortex were remarkably thick—13y. Wheat seedlings 
2 cm. long, atomized with conidia suspension of H. No. 1, in 6 days were 
covered with infection spots over their whole surface. 
Inoculations in soil—Vials 12X70 mm., prepared as described on 
page 180, were used as containers. Wheat seeds were germinated asep- 
tically, and when the shoot was about 2 cm. long they were inoculated 
and transferred to the soil ina vial. The results differed in no essential 
way from those described for the rag-doll inoculations, though the plant 
could be kept longer under observation since it was not solely dependent 
on the seed for food. Aseptic wheat-grains were also planted in these 
vials with the inoculum placed in three different positions: (a) on the seed; 
(b) 1.5 cm. above the seed; (c) 1.5 em. below the seed. When on the seed, 
lesions occurred low; when above the seed, they were higher; when below 
the seed, no lesions were on the stem in early days but the roots were 
heavily infected. 
Duplication, in pots and in benches, of all the above experiments 
made in vials gave identical results. 
Recovery of Organism 
After all the types of inoculation mentioned above, the organism used 
in the inoculation was clearly evident in the tissues and producing conidia 
upon them, and by dilution-plating it was recovered from them. During 
such recovery. there was sometimes evidence of bacterial or other contami- 
nation, but in most cases of each type of inoculation no contamination 
occurred, and the pathogenic changes noted were clearly attributable to 
the fungus used in the inoculation. . 
INFECTLON PHENOMENA ON WHEAT 
Conidia of H. No. 1 and of H. No. 14 when placed on wheat in rag 
doll germinated from one or both ends as described elsewhere. The germ- 
tube grew rapidly, branching freely, and oriented itself lengthwise of the 
shoot more frequently than crosswise or obliquely, often following length- 
wise the boundary between two wheat-cells. At certain places where this 
mycelium touched the wheat-surface it swelled slightly, producing a round 
or oblong appressorium. These appresoria sometimes, probably most often, 
arose by the simple swelling of a cell of the main thread (Fig. 17), though 
frequently also from short lateral branches (Fig. 17, d) or where the terminal 
