PREFACE. 



Under direction of the Board of Trustees, the fourth an- 

 ■ual report of the Missouri Botanical Garden is presented 

 to the public. The first volume of the series was issued in 

 December, 1890, the second in May, 1891, and the third 

 in June, 1892. Reprints of scientific papers, fixing the date 

 of publication of the latter, were issued as follows : Tre- 

 lease, North American Species of Epilobium, April 22, 

 1891 ; Trelease, North American Species of Rumex, April 

 12, 1892; Riley, the Yucca Moth and Yucca Pollination, 

 May 28, 1892; Williams, Fruiting of Parmelia molliuscula, 

 May 28, 1892 ; Trelease, Detail illustrations of Yucca, and 

 description of Agave Engelmanni, May 28, 1892. 



The reports of the Garden are sent regularly to scientific 

 institutions and journals in exchange for publications de- 

 sirable for the work of the Garden, and so far as is pos- 

 sible reprints of the botanical articles which they contain 

 are sent to botanists to whom these papers are directly 

 useful in their work. For the accommodation of persons 

 who may desire the publications of the Garden but feel 

 that they are not entitled to receive them by way of ex- 

 change or as aids to scientific work, a few copies are 

 offered for sale at about the cost of publication ($1.00 each 

 for reports, and 50 cents each for the larger reprints), by 

 Dr. A. E. Foote, of Philadelphia, W. Wesley & Son, of 

 London, and R. Friedlander & Sohn, of Berlin. Application 

 for the exchange of either reports or separate papers may 

 be made to the Director of the Garden. 



William Trelease. 



St. Louis, Jan. 12, 1893. 



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