(4 2 4) 



may not always be combined with other desirable characters. 

 This then might become a problem for the cooperation of the plant 

 breeder. The foregoing statement of the uncertainty and incom- 

 pleteness of methods for the control of these and similar diseases 

 is but an admission that one of the large problems of the plant 

 pathologist is still unsolved. 



PART II 



TAXONOMY OF THE GENUS GYMNOSPORANGIUM 

 5. Introduction 



Some of the species of the genus Gymnosporangium have been 

 known scientifically since the earliest times. The fungus is said 

 to have been mentioned by Franke in his "Speculum Botanicum" 

 in 1638. It is certain that the description of Micheli's Puccinia 

 non ramosa on junipers and cedars given on page 213, and the 

 illustration on plate 92, of his "Nova Plantarum Generum" 

 published in 1729 clearly belong to a species of Gymnosporangium. 

 One of the few species of fungi described by Linnaeus in the first 

 edition of the "Species Plantarum" in 1753 was a Gymnosporangium 

 although of course not referred to by that name, but as a Tremella. 

 Linnaeus had at a still earlier date, 1737, employed the name 

 Byssus for these fungi in his "Flora Lapponica." 



Much work has been done with the group and many papers have 

 been published referring both to the biology and taxonomy of the 

 species. In more recent years since the subject of phytopathology 

 has been receiving considerable attention a great many notes on 

 the economic importance of the group have appeared. The first 

 study of a monographic nature of the genus was made by Farlow 

 in 1880 in a paper entitled "The Gymnosporangia or Cedar-apples 

 of the United States." This, as the title suggests, attempts to 

 describe only American species. Dietel contributed the part on 

 the Uredinales to Engler & Prantl's "Natiirlichen Pflanzenfa- 

 milien" in 1897 in which he devoted three pages to the genus 

 Gymnosporangium. He recognized 14 species in the world, 8 in 

 North America, 5 in Europe, and 1 in India. In 1901, in a brief 

 paper dealing chiefly with the question of nomenclature Arthur 

 recognized 15 species of cedar-apples, of which he said 8 occurred 

 exclusively in North America, 2 in both North America and Europe, 

 3 wholly in Europe, 1 in India and 1 in China and Japan. Descrip- 

 tions of the various species have appeared in Saccardo's "Sylloge 



