Mimicry in two southern weeds 



RoLAXD 'M. Harper 



On a spring day about twelve years ago some acquaintance 

 in Tallahassee, Florida, brought me for identification a living 

 rosette of pinnatifid leaves an inch or less in length. Without 

 flowers or fruit the best guess I could make was that it was a 

 little Cruciferous weed, known at different times as Senebiera 

 pinnatifida, Coronopus didymus, and Carara didyma. If I had 

 been sufficiently interested I could have found where it came 

 from and watched it until it bloomed, but I was too engrossed 

 with other matters, and the weed did not seem important. 



There the matter rested until April 25, 1927, when I found 

 what was evidently the same plant on a roadside near a barn- 

 yard in Dallas County, Alabama. It showed then in the middle 

 of each rosette a sessile head of small woolly achenes. No corolla 

 or stamens could be detected, even in the youngest plants, and 

 I did not even know the family, until specimens were sent to 

 the National Herbarium and New York Botanical Garden, and 

 identified as a species of Soliva or Gymnostyles (Compositae). 

 There was still some uncertainty about the species, on account 

 of rather inadequate descriptions in the books, but a note on 

 the occurrence of the same species in Louisiana, published soon 

 afterward by Prof. Clair A. Brown, ^ and some extracts from 

 the original description, kindly supplied by him, helped clear 

 up the difficulty. 



Since then I have seen it in or near Quincy and Tallahassee, 

 Florida; Thomasville, Georgia; and in Talladega, Tuscaloosa, 

 Autauga, Dallas and perhaps other counties in Alabama; Wilk- 

 inson County, Mississippi; and in a few places in Louisiana 

 (Prof. Brown being with me at some of them in x\pril, 1936). 

 It is probably fairly widely distributed in these states now, but 

 whether it has been there a long time, and been overlooked on 

 account of its small size, or has extended its range lately, it is 

 hard to say. Its favorite habitat is firm soil in dooryards, barn- 

 yards, roadsides, etc., where the grass is sparse or absent; and, 

 like Junciis tenuis, it seems to thrive where people walk on it. 

 It commonly grows in small colonies, with the individual 



1 Torreya,29: 155, 1929. 



104 



