142 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



[Vol. 10 



Black Eyebrow may not depend so much on greater lack of 

 inherent resistance of this variety compared with other varieties 

 as upon the coincidence of favorable weather conditions for de- 

 velopment of the disease and favorable state of maturity of the 

 plants. Infections are most readily accomplished when plants 

 are nearing maturity, and this condition obtained for the Black 

 Eyebrow soybean as the rainy season approached an end. Other 

 varieties, Mammoth, Medium Yellow, Virginia, Wilson, Tar Heel 

 Black, Arlington, Chiquita, Brown, and Tokyo have suffered 

 no damage from this disease. 



Cultural Characters 



The fungus causing pod and stem blight of soybean has been 

 grown on a variety of culture media. An abundance of mycelium 

 with few or no fruiting bodies is formed on agar, while on soybean 

 stems mycelium is usually present in abundance and pycnidia 

 are numerous. Soybean leaf petioles commonly produce less 

 mycelium and larger pycnidia than stems of the same plant. 

 Stems of Melilotus alba prepared and sterilized when the plants 

 have nearly reached maturity give rise to a very sparse mycelial 

 growth and many large pycnidia. In short, the mycelium is 

 more profuse on agar media and the pycnidia are larger and 

 more numerous on petioles of soybean and stems of Melilotus 

 alba. Below is given a brief descriptive account of this fungus as 

 it appears when grown on various substrata. Except in cases 

 otherwise designated, the descriptions apply to test-tube cultures 

 of strains 6, 7, and 14 kept in indirect light at the laboratory 

 temperatures prevailing for the time covered by the dates given. 



Stems of Melilotus alba. — Inoculated August 10, 1921, and 

 kept in a covered glass dish. On August 23, mycelium white, 

 very sparse, the brown color of the stem plainly visible through 

 the thin network; pycnidia very numerous, black, no surface 

 covering of short white hyphae as when grown on soybean stems, 

 exuding spores in milky droplets. December 22, pycnidia num- 

 erous, large, still sporulating, some standing singly, others 

 aggregated in twos or threes; stromatic masses formed on cotton 

 at the bottom of the tube. 



