Brooks : The Fruit Spot of apples 447 







On beet agar. — In stab cultures the growth was umbonate, 



and arborescent [figure 2 (text)]. The hyphae were hyaline 

 with the exception of an olive mass on the surface in the center of 

 the colony. Spores were produced beneath the agar. 



On solution A agar. — The growth was entirely beneath the 

 agar at first. Later an olive stromatic mass developed at the sur- 

 face and from this were produced numerous aerial hyphae. The 

 spores were abundant and were produced beneath the surface 



(PLATE 32, FIGURE 5). 



Miscellaneous media. — Besides the above media the fungus 

 has been grown on various mixtures and under various condi- 

 tions in an effort to produce other fruiting forms. Among the 

 substances used were rice, ground whole wheat, hominy, peptone, 

 corn stalks, and various phosphate and potash solutions. On 

 rice and hominy the growth was white on the surface but olive 

 beneath. On ground whole wheat it was black throughout and 

 gradually turned the wheat to a deep brown. In all peptone mix- 

 tures the culture medium was browned, the greater concentrations 

 being changed most in color. Sodium ammonium phosphate 



the 



added to a sugar solution caused a slimy pink growth to develop 

 instead of the usual coarse olive fungus. 1 This was not true of 

 potassium phosphate. 



The above culture notes show that while the fungus is responsive 

 to changes in food material it is able to make some sort of growth 

 °n almost any medium. 



Acidity. Enzymes. — Since the acidity of the cell-contents of 



a Pple had been considered an important factor in the produc- 

 tion of the "Stippen," it was thought advisable to test whether 

 the fungus in question increased or decreased the acidity of culture 

 media. Thirty ioo c.c. flasks were thoroughly cleaned as for 

 Physiological culture work and 50 c.c. of solution A added to 

 each. After sterilization twenty of these were inoculated with the 

 un gus. All thirty of the flasks were kept under the same condi- 

 tl0ns for sixteen days. At this time the acidity of the inoculated 

 asks ar »d those not inoculated was determined by titrations, 

 he Urge amount of sugar present reduced the sensitiveness of 



l ndicator to such an extent that no definite results were ob- 

 lne d. There had at least been no marked change in acidity. 



