500 Kern: Studies in the genus Gymnosporangium 



of the Gymnosporangia of the United States," by W. G. Fai 



a 



sporangium 



esteliaey by Roland Thaxter f ; 

 sporangium made in 1887 and 



x 



Gymnosp 



pies)," by Roland Thaxter. § Besides these there have appeared 

 numerous other notes dealing chiefly with the economic impor- 

 tance and genetic connection of certain species, the results serving 

 to confirm the facts given in the papers mentioned. 



In addition to ascertaining how many valid species existed in 

 this country, the earlier workers met with the difficulty of deciding 

 how many of these they recognized were like those already 

 described in Europe. With a comparatively small number ot 

 specimens and those from a limited area in the New England and 

 other eastern states, together with incomplete culture data it is 

 not a matter of surprise that some wrong references should be 

 made which might later be explained and adjusted, but which, in 

 some instances, have not been so treated up to the present time. 

 The foregoing is a brief statement of the problems enc0 " n ^ 

 by those who began the systematic study of the genus £;«- 

 sporangium in this country, with an abstract summary of t e pu 

 lished results. Since the date of the last paper mentioned, I 9 - 

 there has been some increase of information concerning the ^ re ^ 

 and a gradual accumulation of specimens in herbaria, but e ^ 

 practically no more available fundamental knowledge, in so 



m 



published accounts are concerned. rTfficulty 



In taking up the study of the group recently, much i^^ 

 was experienced, therefore, and making headway was i |OW 

 partly due to the chaotic condition of the data left y ^ 

 workers, but due also to the fact that it was insufficient w^ ^ 

 into usable form. These difficulties have been met an ^ 



largely overcome, for the present, by the selection o J^^ 

 nostic characters, not heretofore employed, and ? aC ti- 



study and comparison of a large number of specimens r ^^ 

 cally the whole geographical area of the^JnitedStates a 



* Bot. Gaz. ii : 234-241. 1886. 



fProc. Amer. Acad. 22 : 259-269. 1887. 



\ Bot. Gaz. 14 : 163-172. 1889. 



I Bull. Conn. Agric. Exper. Station 107. 1891. 



