132 
show clearly that the mycelium is within, not between, the host cells. 
Penetration into adjoining live cells is attended by the same phenomena 
of penetrating mycelium, “‘callus’’ formation, and wall-changes, though 
appressoria were not observed in such cases, possibly on account of the 
difficulty of observation. Penetration into dead cells is not attended by 
these phenomena. 
The chronological history of a lesion from a simple infection begins 
with the attack on one cell, which is soon overcome and occupied, and at 
24, or, better, 48 hours after inoculation, observation with a 16 mm. 
objective shows regions with one to several cells diseased and browned, 
a 
Fic. 20.—H. No. 1 on wheat: a, mycelium in cells and penetrating the side walls; b, mycelium 
running lengthwise within the wheat cells. 
and the protoplasts undergoing disorganization and becoming browned. 
Owing to the length of the wheat-cells, the diseased regions are much 
longer than broad, and in many instances two diseased cells or two rows 
of them are seen with a quite healthy cell between them (Fig. 21). Under 
action of Javelle water the healthy cells plasmolize beautifully, while the 
sick cells show no plasmolysis. Treated with acid fuchsin in glycerine, 
normal cells show no stain, while in diseased cells the entire protoplast 
becomes pink and the inner lamella, which is swollen, also stains pink. 
This softening and swelling of the lamellae was extensively studied by 
de Bary (8), Ward (123) and Biisgen (30). De Bary, who, in 1886, was 
first to separate a cytolytic enzyme from fungi (Sclerotinia libertiana), states 
that as the inner lamellae undergo partial dissolution they continue for 
a time to give the cellulose reaction, but eventually swell, disorganize, and 
lose this property (8, page 420). He also describes the fungus as growing in 
the middle lamella. Ward (123) describes the cellulose as swelling and soft- 
ening under action of the enzyme produced by Botrytis. Here, too, the 
