Phytologia (Aug 2004) 86(2) 1 1 3 



A NEW COMBINATION IN TEXAS CROTON 

 (EUPHORBIACEAE) 



B. L. Turner 



Plant Resources Center 



University of Texas 



Austin, TX, 78712-0471, USA 



Croton thermophilic (M.C. Johnst.) B. L. Turner, comb. nov. 



Based on C. corymbulosus Engelm.var. thermophilus M. C. Johnst., 

 Southw. Naturalists: 187. 1959. 



Jackie Poole (Botanist, Tx. Parks and Wildlife, pers. comm.) called 

 to my attention that in the Atlas of the Vascular Plants of Texas (Turner et 

 al. 2003; Sida, Bot. Misc. 24) I treated the above taxon as a species, but 

 neglected to make the appropriate format combination in the text itself. 

 This is corrected here. 



Johnston originally described this taxon as a variety of C. corymbulosus 

 Engelm., but latter transferred this to the earlier name C. pottsii (Kl.) 

 Muell. Arg., a widespread, relatively variable, weedy species of the 

 Southwestern U.S.A. and Northern Mexico. As well noted by Poole 

 (Guide to the Rare Plants of Texas, in prep.), C. thermophilus is readily 

 distinguished by its usually markedly fractiflex stems, mostly smaller 

 leaf blades with obtuse apices, and yet other characters. While both 

 taxa may occur in relatively close proximity on southeastern Brewster 

 County, I have not observed intergrades between these, either in the field 

 or in the herbarium (LL, SRSC, TEX), nor have such been noted by yet 

 others 



