A late record for "frost flowers" 



I.. M . DlCKBRSON 



One can hut wonder why the ice crystals or "frost flowers" 

 which form on dried plant stems have so long escaped careful 

 laboratory study unless it is because of the unusual conditions 

 of temperature with which they are identified. It is hoped that 

 the following observations may be of interest to research workers 

 and may suggest possible utilization of this phenomenon to 

 advance our knowledge of plant anatomy and physiology. 



My first observations of "frost flowers" were made on Nov. 

 13, 1934. Several plants were found on the western border of 

 the Cumberland University campus around the stems of which 

 large, symmetrical rosettes of ice crystals had formed. The 

 similarity of these ice ribbons to hoar frost attracted my atten- 

 tion. They were formed on an area beginning about 10 cm. 

 above the surface of the ground and extending up the stem 

 about 6 cm. to 8 cm. The rosettes were from 4 cm. to 12 cm. in 

 diameter. In general the largest rosettes were on the stems with 

 the greatest diameter. 



The plants on which the crystals occurred had shed all seed 

 and leaves and an exact identification could not be made. All 

 were compositae and, I think, of the genus Phtchea. They were 

 under a sparse growth of oak on a gentle slope facing East and 

 slightly protected from westerly and south-westerly winds. At 

 this time the ground was not frozen under the trees and clumps 

 of grass nearby were still green. The bases of the plants were 

 covered by recently fallen leaves. 



"Frost flowers" were again observed on this group of plants 

 on Jan. 3, 1935 and I have found no other record of their occur- 

 rence so late in the season in this latitude. During the previous 

 night the temperature had dropped rapidly and steadily with 

 only a slow atmospheric drift to the eastward. Hoar frost had 

 formed abundantly in open fields and persisted until after 10:00 

 o'clock, A.M. Ice about 4 mm. thick had formed on water in 

 shallow depressions. Examination showed the dried stems to be 

 split radially and in some cases to be broken at the level where 

 crystals had formed previously. Below this region, however, 



57 



