New Combination's 



In order to make the treatment of hosts uniform in the seventh 

 volume of the North American Flora it is necessary to propose 

 a new combination for Euphorbia macropodoides Rob. & Greenm. 

 (Amer. Jour. Sci. III. 50: 164. 1895). It is a Mexican plant, and 

 on a collection of it made by Pringle in the mountains above 

 Cuernavaca, August 4, 1896, has been found Nigredo proeminens. 

 Collections of this Euphorbiaceous rust have previously been 

 reported on three other species of Euphorbia under the segregate 

 name of Zygophyllidmm. For the sake of uniformity the present 

 species of host is here transferred to that genus as Zygophyl- 

 lidium macropodoides (Rob. & Greenm.) comb. nov. 

 ' In establishing the genus Commelinantia in the Bulletin of the 

 Torrey Botanical Club (49:269-275. 1922) Professor B. C.Tharp 

 suggested that in addition to the type species a Mexican plant 

 should be included. A year ago he made a trip to Monterey, 

 Mexico, and secured herbarium material and also living plants, 

 which have since been under observation at Austin, Texas. In a 

 recent letter he writes: " I think there can be no doubt as to its 

 being a valid species, which may be properly included in the 

 genus Commelinantia." As he has sent me a rust obtained at 

 Monterey labelled with the suggested combination, I take this 

 opportunity to place the name on record, as follows: Comme- 

 linantia Pringlei (S. Wats.) Tharp comb. nov. {Tradescantia 

 Pringlei S.Wats. Trans. Am. Acad. 26: 157. 1891). 



J. C. Arthur. 



Purdue University, 

 Lafayette, Ind. 



BOOK REVIEW 



Pennsylvania Trees — Illick* 



The fourth edition of Illick's "Trees of Pennsylvania" ap- 

 peared from the press in March, 1924,* the third edition (1919) 

 having been out of print for some time. The present edition is 

 a book of 237 pages including 119 full-page line-drawing plates 

 illustrative of the trees described on the pages facing them. The 



* Illick, Joseph S., Pennsylvania Trees, Penn. Dept. Forestry Bull. 11, 

 4th edition, 1924, May, 1923, Harrisburg. 



