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, 



FIG. 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 



