133 



mycelium grows in the middle lamella. Jones (71), working with Bacil- 

 lus carotovorus , reports that the enzyme produced, attacks more strongly 

 the middle lamella, but he noted also a softening and swelling of the inner 

 lamella, but found that the cellulose stains (e. g., chlor-zinc-iodide) "give 

 clear blue reactions with these fully softened walls." Van Hall (63), 

 working with Bacillus omnivorus on Iris, reports a similar condition. The 

 inner lamellae, swollen by Helminthosporium, no longer react as cellulose 

 under this test. Blackman and Welsford (18), who describe in detail 

 the entrance of Botrytis cinerea into bean leaves, state that neither before 

 nor after penetration did the staining reactions of the cuticle give any 

 evidence of its being softened or swollen or in any way altered chemically 

 (though the subcuticular walls usually, if not always, swell), and no swelling 



FIG. 21. H. No. 1 on wheat shoots, second day after inoculation. 

 Shaded portion was colored brown. 



of the subcuticular cellulose was observed before the passage of the invad- 

 ing hypha through the cuticle. Pathogenic changes in the inner lamella 

 precede those in the protoplast, that is, no toxin acts upon the proto- 

 plast prior to the swelling of the lamellae. The subcuticular layer swells. 

 Penetration of the cuticle is by pressure. Gardner (58) mentions no 

 changes occurring normally in staining reaction of host cellulose in leaves 

 attacked by Colletotrichum, though in cases of delayed penetration 

 he notes that the cell-wall under the appressorium retained safranin bet- 

 ter than did normal cell-walls. In fruit penetration, however, he found 

 that, characteristically, the inner lamella was so altered as to retain saf- 

 ranin. Ihe action appears to be different in both quality and quantity 

 from that described by Newcomb (86), who, studying enzymes in seeds, 

 states that "with all the ferments the w r alls at first become hyaline, appear 



