130 



cell-wall, and is sometimes simple, sometimes branched. At the place where 

 the penetrating mycelium pierces a wall and enters a healthy wheat-cell 

 there is developed, on the inside of the wheat-cell and surrounding and 

 covering the penetrating mycelium, a callus-like structure (Fig. 17, e-g) 

 which for brevity I shall term the "callus". As the penetratiftg^mycelium 

 continues to grow, the "callus" grows pari passu. Where many penetrating 

 mycelia develop near each other this "callus" may become very large 



L 



J 



FIG. 18. H. No. 1: a, large "callus"-formation, with many penetrating mycelia piercing the 

 cell walls; b, mycelium spreading over the wheat surface, and at many contact points producing 

 appressoria and penetrating mycelia; c, penetrating mycelium of unusual form, and the "callus" 

 rough. 



(Fig. 18, a) and complicated. The "callus" formation seems to be of the 

 nature of a precipitation, probably resulting from toxic action, and a badly 

 intoxicated cell can, in its protoplasmic disorganization, make numerous 

 such deposits at points other than those of mycelial entrance. Thus in 

 some instances the whole inner surface of a cell's walls may be thickly 



