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so, even in fruit. There is not much other difference, except 

 that P. rigida tends to be smaller and with narrower leaves, as 

 if adapted to poorer soils. They both grow in waste places, 

 sometimes together, but the former ranges far to the north- 

 ward, and may have been in Indian clearings before the time 

 of Columbus, while the latter is chiefly confined to Florida, and 

 escaped attention until it was described by Small in 1905. 7 

 Whether it had been there from time immemorial, or was a re- 

 cent introduction from some unknown foreign source, or a recent 

 mutation from P. decandra, we do not know, and perhaps never 

 will know. This is another problem that deserves the attention 

 of geneticists; and readers may recall similar cases in their own 

 neighborhoods. 



Some other closely related pairs of weeds, that often grow 

 in the same habitat, and bloom at the same time, without 

 apparent intergradation or hybridization, are Acalypha virginica 

 and A. gracilens, Plantago major and P. Rugelii, and Specularia 

 perfoliata and 5. biflora. And there may be others in large and 

 more or less weedy genera like Panicum, Paspalum, Cyperus, 

 Euphorbia (and its segregates), Oenothera, Solidago, and Aster. 



University, Ala. 



7 Bull. N. Y. Bot.Gard. 3:422-423, April, 1905. (Type from near Miami.) 



