A PRELIMINARY TREATMENT OF THE OPUNTIOIDEAE 

 OF NORTH AMERICA 



By N. L. BRITTON and J. N. ROSE 



In 1904 the writers began a joint study of the Cactaceae of North 

 America. As early as 1897, however, Dr. Rose had begun to send 

 living specimens to Washington. Through the kindness of Dr. B. T. 

 Galloway, Chief of the Bureau of Plant Industry, and Mr. Frede- 

 rick V. Coville, Botanist of the U. S. Department of Agriculture, ar- 

 rangements were made to properly care for this collection. It has 

 grown until it now comprises about 5,000 individual plants, filling 

 the greater part of a greenhouse 25 by 100 feet. Some 500 plants 

 have died and these have been preserved as skeleton specimens in 

 the U. S. National Museum. Dr. Britton, on the other hand, upon 

 the organization of the New York Botanical Garden, began also to 

 make a collection of living Cacti. He has now accumulated a large 

 study series and a most attractive exhibition series. The latter 

 is especially fine on account of the number of large species, not a 

 few of which are new to our American collections. These two col- 

 lections are very rich in species of Opuntia and allied genera, and it 

 seems desirable to present a preliminary treatment of the group at 

 this time. The species here enumerated are those of which we have 

 actually examined living plants or specimens, or which from our 

 study of descriptions and illustrations there seems every reason to 

 believe should be recognized. Our collections indicate several new 

 species, only a part of which are here described. The type species is 

 Cactus opuntia L. 



We have accepted, in general, the several series of Opuntia as 

 recognized by the late Professor Schumann, but with considerable 

 modification and with several transpositions of species. 



We recognize three genera, belonging to the subfamily Opun- 

 tioideae in North America, including Central America and the West 

 Indies. The species of Opuntia and Nopalea are listed below, while 

 those of Pereskiopsis will be found on pages 331-333 of this volume. 



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