PE.EFACE. V 



forms, which under similar circumstances of soil, &c. would 

 become typical. 



The admirable Monograph of the genus by Professor Eries, 

 of TJpsala (" Symhola ad Misforiam Mieraciorum"), has been an 

 invaluable assistant to me in the determination of species, as also 

 the opinion of that distinguished author respecting a series of 

 specimens transmitted to him for examination. To my friend 

 C. C. Babington I am greatly indebted, not only for a critical 

 examination of my manuscripts, and the opportunity kindly 

 afforded from time to time, for examining numerous specimens in 

 his herbarium, but also by his excellent judgment regarding 

 multitudes of intricate cases. I have also to acknowledge the 

 kindness of Professors Balfour, and G. "Walker Arnott, also of 

 Thos. Westcombe, Daniel Oliver, Jun. and John G. Baker; 

 who, together with Professors Blytt, of Christiania, and Grenier 

 of Besanpon,* have allowed me to inspect their herbariums 

 or given information respecting the result of their researches. 



It is not with any idea that the task is done, that I now 

 venture to publish this little work j but in the hope that it wiU 

 form a nucleus round which further knowledge may be collected. 

 In a tribe so varying, and with which a correct acquaintance can 

 only be gained by careful study of the Uving forms, combined 

 with the evidence afforded by cultivation, new light is constantly 

 thrown upon many species, and much longer time must probably 

 elapse before certain conclusions can be arrived at regarding 

 them. So that should it ultimately prove that some plants here 



* To Professors Blytt and Gienier I am also indebted for a large and 

 valuable series of contiaental specimens. 



