NRW YOK^ 

 liOTANiCAL 



TORREYA 



Vol. iS January- February, 1938 No. 1 



"Frost-flower" plants in Alabama 

 Roland M. Harper 



In a brief symposium on "frost-flowers," by the writer and 

 two others, inToRREVA for August, 1931, it was pointed out that 

 comparatively few species of plants are known to have the prop- 

 erty of producing wings or ribbons of ice on the lower parts of 

 their stems during cold nights. The three papers published at 

 that time, and others there referred to, cited only four genera, 

 Ilelianthemum, Cunila, Pliichea and Verhesina, in three fam- 

 ilies. Another genus and family can now be added to the list. 



Late in November, 1936, I was spending a week-end at a 

 country home in the eastern part of Dallas County, in the black 

 belt of Alabama. About sunrise on the 22nd, a cold frosty morn- 

 ing, my host went out to the lot to attend to his animals, and 

 when he came back to the house he reported that some of the 

 weeds in the garden had ice on them; something he had never 

 noticed before, though he had lived there since 1920. 



As soon as possible I went out to investigate, and found the 

 ice formation to be confined to a single species, Richardia scabra 

 St.Hil., a member of the Rubiaceae, said to be a native of trop- 

 ical America, and known in this country as "Florida pusley" or 

 "Mexican clover." It is rather common in sandy cultivated 

 fields in the southern parts of Georgia and Alabama and the 

 northern part of Florida, and less so in neighboring states. 



Ice formations of this sort previously reported have usually 

 been wavy ribbons about as long as wide, within a few^ inches of 

 the ground. But those on the Richardia were wings, opposite or 

 approximately so, about half an inch wide but extending several 

 inches along the stem and branches. However, if nearness to the 

 ground is essential, the Richardia has the advantage of being a 

 depressed or decumbent plant, and the ice wings extended prac- 

 tically the whole length of the stems, while the species pre- 

 viously reported are erect or nearly so, and seem to exude ice 



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