1 6 Journal of Agricultural Research voi. iv. No. i 



stratum darkens and the pycnidia empty their spore contents to the 

 surface. 



Sterilized tomato stems. — Green tomato stems sterilized in 5 c. c. of 

 distilled water afford a good medium for growth. A whitish cottony 

 mycelium is first seen. This later develops into a dark compact matlike 

 growth which covers the stem and spreads over the surface of the water 

 as a firm pellicle. Within and upon the surface of this mat numerous 

 dark pycnidia develop, and from these the spore masses issue in coils. 

 Microscopical examination of 3 -weeks-old tomato-stem cultures show well- 

 developed hyphae, mature pycnidia, and an abundance of spores. From 

 glycerin slides obtained from these cultures drawings were made showing 

 hyphae, pycnidia, and spores (PI. I, figs. 4 and 7). Spores from tomato- 

 stem cultures varied in size from 3.4 to 5.1 « in length and from 1.7 to 

 2.5/i in width. 



Steamed corn-meal cultures. — In sterilized coni-meal flasks (capac- 

 ity 100 c. c.) growth begins to show in two or three days as a slightly 

 darkened spot. In five days a scant radiating mycelium may be seen 

 and in eight days there is a dark fungous growth 3 to 4 cm. in diameter. 

 Pycnidia are thickly distributed throughout, from the mouths of which 

 slimy spore masses issue in coils. Within two weeks after inoculation 

 the entire surface of the com meal becomes covered with a dark, com- 

 pact, slightly greenish mat of fungus i to 2 mm. in thickness. The sur- 

 face of this mat is pimply in appearance, owing to pycnidial development, 

 and is often thrown into folds or depressions within which the exudate 

 from the pycnidia accumulates (Pi. VI. fig. 2). The pycnidia are sub- 

 globose and vary in color from hyaline to dark brown and black. Single 

 hyphal strands are brownish and contain numerous oil drops. In micro- 

 tome sections made of mature pycnidia, fragile threadlike basidia were 

 seen. Upon these basidia the hyaline i -celled pycnospores are borne. 

 These are subglobular to subcylindrical in shape, i- to 2-guttulate, and 

 vary considerably in size. In older corn-meal cultures (8 to 10 weeks old) 

 the fungous growth becomes crustlike in composition and soot-black in 

 color, breaking easily when touched with a needle. On the whole the 

 best spore production (with scant mycelium) was obtained upon steril- 

 ized corn-meal and tomato-stem cultures. Good mycelial and spore de- 

 velopment occurred on oat, string-bean, and lima-bean agar and upon 

 potato cylinders. 



Beef agar and synthetic agar proved very poor media for the growth 

 of the fungus. 



Characteristic growth upon Melilotus stem, string-bean agar, and potato 

 cylinder is shown in Plate VI, figure i. 



VITALITY OF THE FUNGUS IN CULTURE 



The vitality of the Phoma fungus in culture is good. Transfers made 

 from potato cylinders and string-bean agar cultures 6 to 8 months old 



