PR EFACE. 



Under direction of the Board of Trustees, the twenty-first 

 annual report of the Missouri Botanical Garden is presented 

 to the public. 



The twentieth report, of 1909, was not issued until Jan- 

 uary 14, 1910, because of unavoidable delays in press and 

 bindery; but separates of Dr. Widmann's paper had been 

 issued early in the season, those of Dr. Griffiths' paper on 

 March 22d, and those of the other scientific papers on 

 December 31st. 



These reports are sent to scientific institutions and journals 

 in exchange for publications and specimens desirable for the 

 library, herbarium, laboratories or living collections of the 

 Garden. So far as is possible, reprints of the botanical 

 articles they contain are sent to botanists occupied with a 

 study of the subjects to which they pertain. 



Any of the Garden publications not out of print may be 

 purchased, at approximately the cost of publication, from 

 Messrs. R. Friedlander & Sohn, Berlin, Germany; W. Wesley 

 & Son, London, England; or the undersigned. 



William Trelease. 



St. Louis, Mo., November 15, 1910. 





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