362 Journal of Agricuhural Research voi. vi, no. 10 



however, the ends were cut off to hasten penetration. Strawberry cells 

 are so large that rather thick sections, from 10 to 20M, were found most 

 desirable. The walls of the strawberry cells and of the fungus hyphge 

 are so similar that differential staining was rather difficult. The best 

 differentiation was secured by a combination of methylene blue and 

 clove-oil eosin, using a water solution of tannin as a mordant. This 

 method was suggested to the writer by Mr. Charles S. Ridgeway, of the 

 Bureau of Plant Industry. The hyphse, however, are so large as to be 

 easily distinguished when the sections are properly stained with the 

 more permanent stains, as safranin, Delafield's hematoxylon, or even 

 Bismarck brown. 



RESULTS OF INFECTION OF STRAWBERRIES BY BOTRYTIS SP. 



Botrytis sp. has long been a favorite subject for the investigation of the 

 relations of host and parasite. The somewhat conflicting views held by 

 different investigators as to the nature of its attack on the host are well 

 summarized by Brown ^ in a recent paper. In general, all writers agree 

 on the presence of a cell-wall dissolving enzym, but differ widely as to 

 the cause of the toxic action of the fungus. 



As already stated, strawberries rotted by Botrytis sp. retain their 

 shape, shrivel slightly, and even in a moist chamber there is no evident 

 leaking. The moisture is apparently lost so slowly that it evaporates 

 from the surface of the berry. A microscopic examination shows that 

 the fungus has penetrated all parts of the berry; indeed, the cells are 

 in many places embedded in the mass of mycelium and are apparently 

 held together by it. The fungus is evidently capable of readily dis- 

 solving the middle lamella and of penetrating the cell walls themselves. 

 Often hyphae grow between the cells of the host for some distance and 

 then penetrate the cells (PI. XLIX, A). Not infrequently cells containing 

 numerous hyphae have the shrunken and distorted protoplasmic contents 

 still present (PL XLIX, B, C, D). Sometimes hyphae occur in adjacent 

 cells whose separating wall remains intact and apparently unchanged 

 (PI. XLIX, B) ; or they may pass from one cell into the next, either where 

 the cells are in contact or across an intercellular space (PI. XLIX). 



It is interesting to observ^e that hyphae usually enter a cell at the 

 angle where it joins two other cells; Plate XLIX, D, F, and G, shows 

 examples. The hypha passes between two cells, apparently by dis- 

 solving the middle lamella, and then penetrates the wall of the cell 

 with which it comes in direct contact. Occasionally a hypha seems to 

 push back a portion of the cell wall before penetrating (PI. XLIX, G). 

 The fungus may, however, penetrate the wall at a considerable dis- 

 tance from the intersection of the cells (PI. XLIX, A, E)\ or it may 



1 Brown, William. Studies in the physiology of parasitism. I. The action of Botrytis cinerea. In 

 Ann. Bot., v. 29, no. 115, p. 313-34S- 1915- 



