450 Brooks : The Fruit Spot of apples 



quite persistently. The best results were obtained by staining 

 fifteen or twenty minutes in haematoxylin, washing in acid 

 alcohol until the stain had almost disappeared, transferring to water 

 and then to erythrosin and leaving the slide in the latter stain for 

 several hours. Erythrosin gave fair results when used alone. 

 Free-hand sections were found very serviceable but serial micro- 

 tome sections were generally used. Various thicknesses of 

 sections were tried. Thin ones were best for a study of the 

 stomata and lenticels, but sections 40 to 60 fi thick were found 

 more satisfactory in tracing the mycelium of the fungus. This is 

 not surprising when we bear in mind the large size of the apple 

 cells and extreme fineness of the mycelium. 



Every form and stage of the disease was studied. More than 

 a hundred spots were sectioned and the fungus was found in 

 every spot. This was true of the spots located at stomata and 

 covered by a smooth epidermis as well as of those situated at the 

 lenticels. In the younger stages the fungus had made very scant 

 growth. In several cases it was actually identified in but one or 

 two places in the entire series of sections and these possibly a 

 millimeter or more apart. The threads were hyaline, granular, 

 and apparently non-septate. They were extremely fine, in some 

 cases being less than 1 fi in diameter. They had exactly the 

 same appearance in these young stages of spots as when grown in 

 extremely dilute solutions. 



A study of the later stages showed that the fungus had ac- 

 companied the browning of the tissue in its spread. In the lenticels 

 of the red spots one sometimes found a band of thick-walled pro- 

 miscuously arranged cells passing through the organized layers 

 the lenticel, thus connecting the browned tissue beneath with the 

 break in the epidermis above (plate 32, figure I, and plate 34* 

 figure 4). In such cases the fungus was present in both t c 

 band of cells and the more deeply seated shrunken tissue. Io * e 

 green spots the fungus was found both in the groups of brown 

 cells beneath the lenticel and in those a short distance from 1 

 (P a g e 433)- In many cases it seemed to have remained encys e 

 in the center of these groups of thick-walled cells (plate 3°j 

 figures I, 2). In others it had broken through them, s P rea *^ 

 deeper into the tissue, browning and killing the cells along 



