VI 



ingly given notes on some of them, but in other cases it seemed to 

 us doubtful whether the parasites were really American. 



In the case of genera we have not thought it necessary to give 

 special references except in the case of those peculiar to North 

 America or first described in North America, or in cases where 

 American writers have given critical notes on certain genera found 

 in Europe as well as America. When we have had any reason for 

 differing from other writers as to limits of genera our opinion is 

 given in the form of notes. 



We have endeavored to bring the references as nearly up to date 

 as possible, but it was not practicable to hold in type so large a 

 mass until the whole of the present part was finished. The reader 

 must therefore expect to find the later pages more nearly up to date 

 than the earlier ones, since pages 1-64 were struck off in December, 

 1903, while pages 225 to 312 were not printed until August, 1905. 

 It is proposed to give at the end of the volume the addenda to the 

 earlier pages. The progress of the work has been slow, partly 

 owing to delays to be expected in starting a work of this kind, and 

 also to the fact that the two large and very complicated genera, 

 Aecidium and Agaricus, required a simultaneous arrangement of 

 other genera to appear later. 



A word should be said as to the system of classification and the 

 limitations of genera and species which we have followed. In 

 general, while giving as much information as we were able, we have 

 tried as far as possible to avoid changing names in common use for 

 many years. At the present day the Sylloge of Saccardo and the 

 Pfianzenfamilien of Engler and Prantl may be said to be the two 

 works on the classification of fungi in most general use, and we have 

 preferred to follow them as far as possible, making the changes 

 required in consequence of information obtained either from recent 

 critical monographs by those who have made a special study of 

 different orders and genera or from our own examination of Ameri- 

 can material. We are quite ready to admit that the present classi- 

 fication of fungi is not one which can be called more than temporary, 

 but the time has not arrived when our knowledge of the fungi of the 

 world is sufficiently advanced to make it possible to form a really 

 natural and scientific system. 



We have followed the principle of adopting the oldest specific 

 name under which a species was described. We cannot say that 



