of Ice round the decaying Stems of Vegetables during Frost, 111 



stumps of a bed of heliotropes, which had been left out to try 

 the chance of the season, were found to be affected with a 

 similar and very copious accumulation of ice to what I had 

 before observed round the thistle-stalks. Fig. (A), Plate II. 

 shows the general appearance of this accumulation ; while the 

 mode in which it was attached to the stem, and seemed to 

 emanate in a kind of riband- or frill -shaped wavy excre- 

 scence,— as if protruded in a soft state from the interior of the 

 stem, from longitudinal fissures in its sides, — is exhibited at 

 fig. (B). The structure of the ribands was fibrous, like that 

 of the fibrous variety of gypsum, presenting a glossy silky 

 surface ; the direction of the fibres being at right angles to 

 the stem, or horizontal. 



Although, as remarked, the icy sheets appeared to have been 

 protruded from the interior of the stem, yet on examination 

 they were found to terminate sharply at its surface, adhering 

 to it so lightly as to render it impossible to handle a specimen 

 without detaching them, and in no instance connected with 

 any formation of ice within ; on the contrary, the majority of 

 the stems were sound and solid, and many of them still green 

 when cut. The point of attachment of the ice was, however, 

 always on the surface of the wood, beneath the outer bark or 

 epidermis, which the frozen sheets had in every instance strip- 

 ped off, and forced out to a distance. Where the fringes 

 were large and well developed, the bark had quite fallen off; 

 but in those cases where it adhered more strongly, it seemed 

 to have prevented their free expansion ; and in such instances 

 the stem presented the singular appearance (C) of a thick 

 massive coating of ice interposed between the wood and its 

 integument, which was swollen and rifted. 



The appearances above described are quite at variance 

 with any idea of the deposition of these icy fringes froni the 

 store of aqueous vapour p in the general atmosphere, in the man- 

 ner of hoar-frost ; and the only quarter to which we can look 

 for their origin is in the plant itself, or in the comparatively 

 warm earth beneath, to whose exhalations the decaying stems 

 may form a kind of chimney. In the present instance, the 

 season had been, up to the night in question, uncommonly 

 mild and open ; and the frost of a single night being insuffi- 

 cient to penetrate far into the soil, it may easily be supposed 

 to have been giving out moisture through every open spiracle. 

 What share the physiological functions of the plant may have 

 in the phenomenon, or whether it be connected with the vi- 

 tality of the stem at all, it is for botanists to decide. 



I remain, Dear Sir, your very obedient Servant, 

 January \2, 1833. J. F. W. HERSCHEL. 



