OF ARTS AND SCIENCES. 213 



XV. 

 CONTRIBUTIONS TO AMERICAN BOTANY. 



By Sereno Watson. 



Presented May 14, 1879. 



I. Revision of the North American Liliacece. 



The order Liliacece, as outlined by Dr. Gray in the last edition of his 

 Manual (1867), and as now generally understood by botanists, pre- 

 sents such a diversity in its characters and their combinations that it is 

 by no means easy to satisfactorily group the genera according to their 

 affinities, or to arrange them in any seemingly natural sequence or 

 sequences. The difficulty is not much diminished, but rather increased, 

 when the question is confined to the genera of a limited geographical 

 area ; hence, in the following attempt at a classification of the fifty 

 genera that are found in North America, their relations to the rest of 

 the order have been in some measure taken into account. 



If the character of a baccate as distinguished from a capsular fruit 

 be considered a subordinate one (as seems to be necessary), a division 

 of the genera may be made into three series or suborders, which, 

 notwithstanding exceptions, are on the whole pretty clearly defined. 

 The first and largest of these is prominently distinguished by its 

 scarious floral bracts, persistent nerved perianth, perigynous stamens 

 with introrse anthers, an undivided persistent style, and a loculicidal 

 fruit (if capsular). This includes much the larger portion of the 

 genera which have usually been considered as belonging to the capsu- 

 lar Liliacece, as well as most of the Asparaginece. Both of the other 

 divisions have the stamens hypogynous or nearly so, with more or 

 less extrorse anthers, and the floral bracts are more or less foliaceous 

 or are wanting. Both also always have distinct perianth-segments 

 and unjointed pedicels. But one has a nerveless deciduous perianth, 

 the styles (when present) more or less united, and the fruit a loculi- 

 cidal capsule or a berry ; to this belong the Liliece or Tulipece proper, 

 the Uvulariece and the Trilliece, as here defined, and a few other 



