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 
Fic. 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. The 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 walls at first become hyaline, appear 
