HORTICULTURAL SOCIETY OF NEW YORK. 



THE CLx\SSIFICATION OF CACTACEiE 



BY N. L. BRITTON, APRIL 12, I904. 



The grouping of the species of cactuses into genera has been one of the 

 most difficult problems of systematic botany, because this classification has 

 necessarily been based largely on the plant body alone, inasmuch as the flowers 

 and fruits of many of the species have either been unknown to botanists or 

 imperfectly understood. It has been known that certain features of structure 

 of the plant body are associated with characters of the flowers and fruits, and 

 that if these were known in all the species, a truly scientific grouping could 

 be established. As everyone who has grown cactuses knows, many plants will 

 remain alive in collections for years without making any considerable growth 

 and without flowering; herbarium species, prepared either from plants in 

 their native haunts or from those in collections, are in many instances unsat- 

 isfactory for study, because they can, at the best, be but fragmentary. Herbarium 

 specimens supplemented by flowers and fruit preserved in formalin, by photo- 

 graphs of the flowering plant and by colored drawings of the flowers, are 

 satisfactory taken in connection with the living plant, and if such series of 

 material of each species can be brought together, it will ultimately lead to a 

 far better understanding of this very interesting family. 



The preparation of manuscripts for the "North American Flora," now in 

 course of publication by the New York Botanical Garden, through the aid of 

 the David Lydig Fund, bequeathed by Judge Charles P. Daly, has made it very 

 desirable that a more accurate knowledge of the cactuses of North America 

 should be obtained within the next few years, and the bringing together of the 

 material along the lines outlined has been undertaken in co-operation with 

 Dr. J. N. Rose, of the U. S. National Museum, greenhouses at Washington and 

 at New York have been set aside for the housing of the plants, and exploration 

 of the cactus-yielding regions of North America, including the West Indies and 

 the continent south to the Isthmus of Panama, is going forward and will be 

 continued as rapidly as means for it become available. 



The lecture was illustrated by lantern slides selected to bring out the principal 

 features of the various groupes of cactaceae, and numerous modifications of 

 currently accepted generic limits were indicated. 



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