Junes, i9i6 Histology of Strawberries 365 



Fungus hyphae were found in all parts of the berry, being abundant 

 even in the center, within the circle of vascular bundles. Apparently 

 the extreme dryness of the surrounding air made the intercellular spaces 

 within the berry more favorable for its growth than the outer ones. 

 Under these severe conditions the cells of the berry collapsed so generally 

 that the relations of the fungus hyphae to the walls could usually be 

 studied only in cells near vascular bundles. It was evident that while, 

 in general, the hyphae grew between the cells of the host (PI. L, L) they 

 were frequently found inside the cells as well (PI. L, K, M). It is worthy 

 of note that in these berries several instances were found where hyphae 

 had punctured the cells and the nucleus of the cell was unchanged in 

 appearance (PI. XLJX, K). 



COMPARISON OF THE FUNGI 



The difference in the histological relations of the two fungi with the 

 strawberry may be briefly summarized as follows : 



Botrytis sp. penetrates all parts of the berry, growing within the cells 

 as well as between them and ramifies through the tissues of the strawberry, 

 surrounding and filling them with a network of mycelium. The cells of 

 the berry seem to be quickly killed by the fungus; at least the proto- 

 plasm shrinks away from the cell wall and becomes disorganized so that 

 no nucleus can be distinguished. 



The mycelium of Rhizopus sp., on the other hand, is found chiefly in 

 the outer portion of the berry. The hyphae grow between the cells, 

 separating them and apparently extracting the cell sap. The nuclei of 

 the cells persist unchanged until a late stage in the breaking down of the 

 cytoplasm. When the fungus is grown on berries in a dry atmosphere, its 

 action is somewhat different. The mycelium penetrates to the center 

 of the berry, and hyphae are frequently found inside cells. 



It is difficult to trace an exact causal relation between the histological 

 differences in the attack of these fungi on the strawberry and the fact 

 that they cause quite different types of rot. The fact that Rhizopus sp. 

 separates the cells of the berries so completely may readily account for 

 the berries affected with this fungus becoming so soft and easily flattened. 

 On the other hand, the mycelium of Botrytis sp., by penetrating all parts 

 of the strawberry, helps to hold it in shape and converts it into a mummy. 

 It is possible that the juice of the berries affected by Rhizopus sp. is 

 pressed out by the collapse of the berries, owing to the mere separation 

 of the cells. This is, however, hardly an adequate explanation of the 

 phenomenon. 



While it is not proposed at the present time to review the rather 

 voluminous literature on either of the fungi under consideration, a 

 closely parallel case described by Behrens * should be mentioned in this 



' Behrens, Johannes. Beitriige zur Kenntnis dcr Obstfauhiis. In Ccntbl. Bakt. [etc.], Abt. 2, Bd. 4, 

 No. 12, p. 515-516. 1S98. 



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