Jan. 1908] Cultures of Uredineae in 1907 1 8 19 



Cultures of this species were made by Prof. W. G. Farlow, 2T 

 in 1883, from teliosporic material on Juniperus Virginiana, which 

 gave rise to pycnia on leaves of Malus Mains, Aronia arbutifolia 

 and Amelanchier Canadensis, but failed to mature aecia. Cult- 

 ures were also made by Dr. Roland Thaxter 28 in 1886, from 

 similar material, producing pycnia on leaves of Malus Malus, 

 and both pycnia and well developed aecia on Amelanchier 

 Canadensis, especially on stems and midribs. A difference in 

 the source of material used in the earlier cultures, and for the 

 present year, is worth noting. The former was taken from 

 Juniperus Virginiana, the red cedar, while the latter came from 

 Juniperus Sibirica, the dwarf juniper. This is the only species 

 of Gymnosporangium so far known to inhabit both the true 

 cedars and the true junipers, and the situation should receive 

 careful study. Either the species is a more generalized one than 

 usual, which is not borne out by the geographical distribution, 

 or it is an aggregate of two closely related forms thus far 

 confused. 



21. Gymnosporangium clavariaeforme (Jacq.) DC. 

 Teliosporic material on the stems of Juniperus Sibirica Burgsd., 

 obtained at Lake Forest, 111., by Mr. F. D. Kern, was sown on 

 leaves of Malus Malus (Bechtel Crab variety), with no infec- 

 tion, and also on leaves of Amelanchier intermedia April 11, 

 giving rise to a few pycnia April 20, but to no further develop- 

 ment owing to withering of the leaves. 



The first culture of this species was made in Denmark, by 

 Oersted, in 1867. The numerous subsequent cultures by Euro- 

 pean investigators are summarized by Klebahn. 29 The only 

 definite cultures with American material were made by Dr. 

 Roland Thaxter, 30 in 1886 and 1887. He grew an abundance 

 of pycnia and aecia on Crataegus tomentosa and Amelanchier 

 Canadensis. Uncertain results were obtained in trials by Prof. 

 L. H. Pammel. 31 



22. Gymnosporangium nidus-avis Thax. Teliosporic ma- 

 terial on Juniperus Virginiana L., obtained at Lake Forest, 111., 

 by Mr. F. D. Kern, was sown on Amelanchier intermedia, with no 

 infection, and also on Malus Malus (Whitney Crab variety) April 

 10, which gave rise to a few pycnia April 17, and aecia May II, 

 a period of incubation shorter than for most Gymnosporangia. 

 The spores for sowing were taken from large sori on the branches. 

 The only previous cultures of this species were made by Dr. 



"Proc. Am. Acad. Sci. 20 :313. 1885. 



M Bot. Gaz. 11:236. 1886; Proc. Am. Acad. Sci. 22:264. 1887. 



a Die wirtswechselnden Rostpilze, pages 339-345. 



80 Proc. Am. Acad. Sci. 22:262. 1887; and Bot. Gaz. 74:166. 1889. 



"Bull. Iowa Exper. Sta. 84:33. 1905. 



