536 Report op the Mycologist op the 



In the United States there are nine species of Gymnosporan- 

 gium. Chiefly through the investigations of Drs. Farlow and 

 Thaxter all of them have been connected with their corresponding 

 species of Hoestelia. 



Gymnosjporangium macropus, Lk., the particular species under 

 consideration, is confined exclusively to the red cedar, Juniperus 

 Virgmiana, L. Its Hoestelia form is known as Hoestelia pirata, 

 Thax., and is found on cultivated apple {Pirus malus, L.), wild 

 crab {Pirus coronaria, L.) and Juneberry [Amelanchier). The 

 Gymnosporangiiiin may be found in the autumn upon the twigs of 

 red cedar where it appears in the form of small brown balls about 

 the size of peas. In May of the following spring these balls en- 

 large and during rainy weather put out several orange-colored, 

 gelatinous horns. At this time the balls are very conspicuous 

 objects and are universally known as " cedar apples." The gelatinous 

 horns contain numerous two-celled spores on long pedicels. The 

 spores germinate in situ, each one producing several minute second- 

 ary spores which are readily carried by the wind. When these 

 secondary spores chance to .fall upon the leaves of apple or other 

 suitable plant, they germinate and enter the tissues. In about three 

 weeks, small yellow spots appear on the npper surface of the apple 

 leaf. This is the Roestelia, and when it is mature the spots will be 

 one-fourth to one-half inch in diameter, yellow above and with 

 tooth-like projections beneath. Within the projections are formed 

 round one-celled spores (aecidiospores) which may be carried to a 

 cedar where they will germinate and repeat the life cycle. 



The connection of Gymnosporangium macropus with Roestelia 

 pirata has been established beyond question by Dr. Thaxter. i The 

 inoculation experiments here reported were not undertaken for the 

 purpose of obtaining further information concerning the relation- 

 ship existing between the two forms of the fungus, but rather to 

 ascertain why the cultivated apple in central Iowa should be free 

 from Roestelia. Although the field has been thoroughly canvassed 

 nearly every season during the past twenty-five years, no species of 

 Roestelia has ever been taken on any variety of cultivated apple in 

 the vicinity of Ames, lowa.^"- More than this, repeated efforts to 



1 On certain cultures of Gymnosporangium with notes on their EoesteUae, Am. Acad. Arts 

 and Sciences, 1886, p. 259. 



1 a Prof. Pammel writes tliat he has never known or heard of Roestelia on any cultivatep 

 variety of apple in Ljwa. 



