No. 433-] NOTES AND LITERATURE. 



75 



has become excessive, every piece of monographic work based upon 

 prolonged study of a particular group and passing mature and con- 

 nected judgment upon all its species is a welcome addition to 

 scientific literature. This is especially true of Professor Trelease's 

 work on the Yucceae from the fact that it treats a group of natural 

 difficulty, in which, as in the case of the palms, cycads, Cactacese, 

 and other large and succulent plants, ordinary herbarium methods 

 are least effective and must to a great extent be supplemented by 

 the slower and far more difficult process of visiting the growing plants 

 in their native habitats or cultivating fresh material. The paper 

 under consideration is an octavo of 133 pages, copiously and excel- 

 lently illustrated by 100 plates, the latter being chiefly halftones 

 from photographs. The work presents "the principal conclusions 

 reached in an intermittent herbarium, garden, and field study extend- 

 ing over the last sixteen years, in the course of which nearly all of 

 the spontaneous species have been examined and photographed in 

 their native homes." 



The author divides the Yucceae into five genera. The genus Yucca 

 is confined to those species which possess globose or broadly cam- 

 panulate flowers with a thin polyphyllous perianth and a short thick 

 or obsolete style. From Yucca, which includes twenty-seven species 

 and may be regarded as the central and typical genus of the group, 

 Hesperaloe, with two species, is distinguished by its narrow perianth, 

 Hesperoyucca (monotypic) by its filiform style, Clistoyucca (mono- 

 typic) by its thickened perianth, and Samuela, with two species, by 

 its gamophyllous perianth. Yucca is divided upon the nature of the 

 fruit and seed into three sections: Chasnoyucca (the filamentosa 

 group), Heteroyucca (the gloriosa group), and Sarcoyucca (the bac- 

 cata group). 



Under each species and variety exhaustive bibliography and syn- 

 onymy are given. These cover not merely the botanical treatment 

 of the plants concerned, but also the far more involved and vague 

 horticultural references, and the frequency with which the mark of 

 interrogation accompanies the citation of synonymy is certainly 

 significant. Here an energetic specialist, exceptionally situated for 

 the thorough investigation of his group and engaged in the revision 

 of not over thirty or forty species, finds himself, even after some six- 

 teen years' effort at the elucidation of his group, obliged to use no 

 less than ten question marks in stating the synonymy of a single 

 species. A few of these doubts refer, as might be supposed, to old 

 and vague characterizations published by the earlier authors, who 



