4 ROCHESTER ACADEMY OF SCIENCE. 



answer to any species described in the botanies, there was apparently 

 no way in which they could be disposed of except to consider them 

 as variations from the types, and in our former list of plants only six 

 species were given. These were all that could be expected to be 

 found in our locality, according to the Sixth Edition of Gray's Botany. 



In 1899, Mr. John Dunbar called the attention of Dr. Charles S. 

 Sargent, of the Arnold Arboretum, to this subject, with the result 

 that Dr. Sargent, assisted by a number of our botanists, began a 

 careful and systematic study of the thorns of this vicinity. Hundreds 

 of specimens of flowers and fruit have been collected and forwarded 

 to Dr. Sargent for examination, and he has made numerous visits to 

 Rochester to examine types. Seeds of more than two hundred 

 specimens have also been collected and sent to Dr. Sargent; these 

 have been planted and are now growing on the grounds of the 

 Arnold Arboretum. 



This study of the Crataegus has been carried on unremittingly 

 since 1899, with the result that seventy-nine species found growing 

 within our limits have been named by Dr. Sargent. These will be 

 found on pages 12-17 o^ this list. 



Mr. C. C. Laney, Mr. John Dunbar, Mr. M. S. Baxter, Mr. V. 

 Dewing, Mr. Henry T. Brown and Mr. Bernard Slavin have been 

 enthusiastic workers in this field, and to their untiring labors, supple- 

 menting that of Dr. Sargent, is due the large number of new species 

 which have been found and named. Dr. Sargent notes that the 

 lower valley of the Genesee is remarkably rich in species of Crataegus, 

 and as the work is still being carried on, it is probable that further 

 additions may be made to the list. 



We are aware that a few botanical authorities doubt the validity 

 of some of these numerous species, regarding them as mere varieties. 

 But as they have been most carefully studied and named by the very 

 best authority on the genus ; have been repeatedly grown from seed 

 and remain constant to type and seem true species according to all 

 recognized tests ; and their validity having been recognized by a major- 

 ity of the eminent botanists of America, we have no hesitation in giving 

 all of those which have been found growing within our limits their 

 proper place in our list. 



Descriptions of these new species, or reference to the original 

 publication, down to 1907, may, with few exceptions, be found either 



