370 Journal of Agricultural Research voi. v.No.g 



Gold is a thin-skinned susceptible variety. Sultan is not known to the 

 writer. 



The three varieties designated "S. D. Nos. i, 2, and 3" are varieties 

 obtained from Mr. A. Brackett, of Excelsior, who received them from the 

 South Dakota Experiment Station. Their true names were not known 

 to Mr. Brackett. S. D. No. i is a thin-skinned variety and rotted badly 

 on the trees when sprayed once with Bordeaux mixture. S. D. Nos. 2 

 and 3 were thicker skinned, firmer varieties and did not rot after one 

 spraying, many fruits drying on the trees. All appear to be sand-cherry 

 hybrids. 



Compass, a hybrid between a sand cherry and P. americana (Hansen, 

 191 1 ), is a thin-skinned variety which becomes soft on ripening and is 

 susceptible to the brown-rot. Reagan, a hybrid of Wayland {P. hortu- 

 lana) X P. americana (Hedrick, 191 1) is thick-skinned, very firm when 

 ripe, and is very resistant to the rot. Specimens of the ripe fruit used 

 were received from the New York Experiment Station, Geneva, N. Y, 



Ocheeda and Harrison are varieties of P. americana. Manitoba No. i 

 is probably a variety of P. nigra. Hammer is a hybrid between P. hor- 

 tiUafia mineri and P. americana (Hedrick, 191 1). These varieties were 

 obtained from the orchard at University Farm. 



TAXONOMY OF THE FUNGUS 



MONILIA STAGE 



The brown-rot fungus in Minnesota is found for the most part affecting 

 plums, but to a very limited extent also attacking the apple. It appears 

 on the plum first as a small brown or purple spot, which increases very 

 rapidly in size. In a very short time the spore tufts appear irregularly 

 over the surface of the rotted area. These are usually small and ashen 

 gray in color, although in many cases the color varies to a yellow ocher. 

 Plums inoculated through a wound made by cutting off the tip of the 

 fruit, when allowed to rot under a cardboard box in nearly total darkness, 

 produced spores of a bright-ocher color over the wounded area and in 

 some cases through the skin. Mummies collected from trees in the late 

 fall showed spore tufts which varied from gray to* a light ocher. The 

 chlamydospores of the local form, taken from mummies which have 

 hung on the trees over winter, retain their power of germination. 



Chlamydospore measurements were made of spores from Soulard and 

 Eongfield apples, from Harrison, Ocheeda, Newman, and Surprise plums, 

 which were rotted in the laboratory, and from a culture on beerwort 

 agar. In each instance 100 spores were measured, except in the case of 

 the beerwort-agar culture, where 50 spores were measured. The results 

 are given in Table I. 



