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THE GENUS CRATMGUS IN NORTH AMERICA. 



By Prof. 0. S. Sargent, F.L.S. 



Fifteen years ago American botanists recognized fourteen 

 species and a few supposed varieties of North American Cratcegus. 

 These, with a few exceptions, had been described in Europe, and 

 chiefly from cultivated plants ; and the arrangement of the species 

 published in 1838 by Torrey and Gray in their Flora of North America 

 has been practically adopted in subsequent publications on the 

 American flora. In 1882 Engelmann, however, described C. brachy- 

 acantha, a blue-fruited species of Louisiana and Texas, first collected 

 many years earlier by Drummond; in 1892 Chapman described 

 two species which he had found at Rome, in northern Georgia; and 

 in 1896 Green published his very distinct G. Maligna of the Rocky 

 Mountains. About this time our interest at the Arboretum in the 

 genus was roused by the fact that plants raised here from seeds col- 

 lected in various parts of the country differed constantly from any 

 of the described species. It was soon seen that different plants 

 which it had been supposed belonged to one species differed in their 

 time of flowering, in the number of their stamens, in the colour 

 of their anthers, in the time of the ripening of their fruit, and in 

 the nature of the fruit and the form of the nutlets, and that these 

 characters were constant and could be depended on as distinguish- 

 ing characters. 



Following up the investigation, it was found that these seedling 

 plants in the Arboretum were identical in all these characters with 

 the wild plants from whose seeds they had been raised. These 

 facts led to a more careful study of the genus in several States, with 

 the result that about five hundred species have been described in 

 the last eight years. It is not surprising that botanists, looking at 

 the genus through the eyes of Torrey and Gray, or reaching their 

 conclusions from the study of the scanty and generally incomplete 

 material found in herbaria, have regarded the makers of all these 

 species with pity, and have tried to throw ridicule on this investi- 

 gation and its results. To those persons, however, who examine 

 the plants in the field even casually, the fact is soon apparent that 

 the genus contains many very distinct forms, whether these are to 

 be called species or not. 



These distinct forms or species fall into twenty natural groups, 

 and the plants of these groups cau be recognized at a glance. For 

 botanists with broad ideas in regard to the limitation of species the 

 twenty groups may represent twenty species, under each of which 

 can be grouped a number of subspecies and varieties, while other 

 botanists may consider it more convenient to treat all distinct 

 forms as species. The Pnrinosa group, based on a cultivated plant 

 described by K. Koch in 1854, and until recently entirely over- 

 looked by American botanists, will serve perhaps to illustrate the 

 varieties which are now known to occur in one of the large groups. 

 The Pruinosce are distinguished by their late-ripening, often green, 

 sometimes angled and generally pruinose fruit, large flowers, and 



Journal of Botany. — Vol,. 45. [August, 1907.] y 



