SCIENCE 



NEW YORK, DECEMBER 29. 1893. 

 EROST PLANTS: A RESUME. 



BY D. T. MACDOUGAL, UNIVERSITY OF MINNESOTA. 



Pkof. Lesteb F. Ward's observations ou the "Frost 

 Freaks of the Dittany," in the Botanical Gazette for April, 

 1893, obtain more than a passing interest, since the 

 phenomenon recorded — ever but little noticed, and re- 

 cently almost forgotten — illustrates one form of the ac- 

 tion of the woody tissues, and the medullary rays, in 

 the movements of water in the plant stem. 



Since the article mentioned and the accompanying cut 

 may not be accessible to all of the readers of Science, it 

 may be pertinent to say that the frost phenomena of this 

 and other jJlants consist principally of the formation of 

 very thin sheets of crystals of ice on the sides of the stem 

 near the ground. These crystals are attached only by 

 one edge, and extend their length of several inches out 

 into the air in a sinuous or scroll-like form. The inter- 

 pretation of the facts affording this jjhenomenon seems to 

 the author to be of such importance as to justify their 

 presentation here. 



The first observation recorded is that of Stephen Elliot, 

 who "notices a remarkable protrusion of icy crystals from 

 the stems Couyza bifrons" (now Pluchea bifrons). (1824. 

 Sketch of the Botany of South Carolina and Georgia, Vol. 

 2, p. 322.) 



Sir John F. Hei'schel notices a similar occurrence on 

 the stalks of the thistle and heliotrope, in the London and 

 Edinburgh Philos phical Magazine (1833. 3d series. 

 Vol. 2, p. 110). 



Prof. S. R. Rigaud notices the analogous formation of 

 ice crystals on a newly-built stone wall, in the same jour- 

 nal (1. c. 13. 190). 



The frost freaks of the dittany were first noticed bj- 

 Dr. Darlington in his '-Flora Cestrica"' (1837. p. 3.50). In 

 his description of the C'unila Mariana (the dittany) he 

 says: "In the beginning of winter, after a rain, very 

 curious and fantastic ribands of ice may often be ob- 

 served attached to the base of the stems of this jslant, 

 produced, I presume, by the moisture from the earth 

 rising by capillary attraction, and then being gradually 

 forced out horizontally through a slit by the process of 

 freezing The same phenomenon has been noticed in 

 other plants." Referring to Helianthemum Canadense, 

 he says: "Prof. Eaton and Dr. Bigelow have noticed the 

 formation, in freezing weather, of curiously curved ice 

 crystals near the root of H. Canadense" (1. c. p. 314). 



Prof. John Leconte made a study of the frost phe- 

 nomena of Fluchea bifrons and P. camphoraia Decand., in 

 November and December, 1848, along the coast of South 

 Carolina and Georgia. The results of his observations, 

 and a consideration of the results of some of the j)re- 

 ceding workers, are given in the Proceedings of the 

 A. A. A. S. for 18.50, under the title of "Observations on 

 a Remarkable Exudation of Ice from the Stems of Vege- 

 tables, and a Singular Protrusion of Icy Columns from 

 Certain Kinds of Earth During Frosty Weather." 



The frost phenomena noted by these several observers 

 on the various plants agree in their general features, and 

 it is only necessary to present the conclusions reached by 

 Leconte in his lengthy and detailed consideration of the 

 subject. The points which apj^ear to be well established 

 are: 



1. The ice crystals on any plant are in the form of 

 sheets, one to five in number, about three or four inches 

 in width, and extending one to five inches from the plant. 



2. The crystals are attached in longitudinal lines, fol- 

 lowing the medullary rays, in the portion of the stem 

 immediately above the ground, around which they are 

 arranged symmetrically or unsymmetrically. 



3. The crystals ai^pear to have their origin at the 

 outer surface of the flbro-vascular ring, and protrude 

 through slits iu the bark, which has been ruptured in 

 their formation. If the bark is strong enough to resist 

 this rupture, the ice extends around the plant in the form 

 of a thin laj'er of ice between the wood and bark. 



4. When the crystals did not extend into the woody 

 ring, they might apjjear in the same i^osition several days 

 in succession : if, however, the crystals extended through 

 the wood along the rays, the wood split apart in the 

 freezing, and no more crystals could be formed at that 

 23lace. 



.5. The stems had ceased growing and were in all 

 stages, from almost green to entirely dead ; in all cases 

 the stems were more or less saturated with water. The 

 phenomena is entirely physical : similar formations are 

 exhibited by certain soils. 



G. The crystals are formed in the greatest profusion 

 immediately after rainfall, and at a temperature slightly 

 below 30° F. 



All of these conclusions are fully warranted by the facts 

 recorded, but when Professor Leconte sought an explana- 

 tion of the actual movement of water in the plant 

 stem necessary for the formation of the crj'stals, 

 he was, of course, limited by the somewhat crude know- 

 ledge of plant anatomy current at that time. His reason- 

 ing that i^liii^ts to show frost phenomena must be 

 annual and herbaceous is entirely at fault, since the very 

 plants upon which he worked are described by many 

 botanists as biennials, as well as Helianthemum, on which 

 the phenomenon is most frequently noticed. Again, 

 while herbaceous stems doubtless furnish these crystals 

 in greater profusion, the stem of Helianthemum is very 

 woody and hard, with a relatively small section of pith. 

 He reasons that the water "is drawn upward through the 

 highly porous pith, while the wedge-shaped medullary 

 raj's secure the mechanical conditions necessary for the 

 projectile force in the proper direction." 



Of course, the water is drawn upward through the ves- 

 sels near the ijith, and is conducted laterally by the 

 medullary rays. That the fluid does take this course in 

 the dead stems was proven by the author, by allowing 

 them to absorb and carry ujj colored solutions. It ap- 

 jsears that the water is taken up by the simple saturation 

 of the roots from the charged soil, without the interven- 

 tion of the special activity of the root hairs, as is shown 

 by the fact that plants dug up and replanted, which 



