332 Dr. LeConte on a remarkable Exudation of Ice 



swollen and rifted." To the foregoing very accurate descrip- 

 tion I have only to add, that, according to my observations on 

 the Pluchea, when the frost is quite severe, the icy sheets isoere 

 often " connected with the formation of ice within," in fact, 

 were continuous with the frozen pith ; but under such circum- 

 stances the wood was always rifted longitudinally, and the 

 process of protrusion seemed to have been completely checked 

 at the part of the stem in which this took place. Indeed, the 

 phaenomenon was seldom exhibited in its most perfect and 

 beautiful form when the wood was split. It is obvious, there- 

 fore, that in these instances the frigorific action was too in- 

 tense to permit the phaenomenon to be developed in a normal 

 manner. 



4. The phaenomenon took place in the same plajit during 

 several consecutive nights; and when the wood was ;/o^ rifted, 

 frequently from the same portion of the stalk. When the 

 wood was split, however, the deposition of ice occurred lower 

 down the stem, at a part which was unaffected by the frost of 

 the previous night. The stalks thus became completely rifted 

 by a succession of severe nights, from tiie height of six or 

 seven inches down to the ground. This is unquestionably 

 one of the reasons why these exudations of ice are seldom 

 observed after the middle of winter, for the stalks are usually 

 destroyed before this period, 



5. The stems which had been cut off within three or four 

 inches of the earth exhibited the phaenomenon as conspicu- 

 ously as those which were left untouched. The icy sheets 

 never issued from the cut surface, but always from longitudinal 

 lines commencing somewhat below it and extending towards 

 the root. Plants which were torn up and transplanted in a 

 box of moist earth in a flower garden exhibited the same phae- 

 nomenon, although much less strikingly than when left in situ. 



" The appearances above described," to use the language 

 of Sir John Herschel, " are quite at variance with any idea 

 of the deposition of these icy fringes from the store of aqueous 

 vapour in the general atmosphere, in the manner 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." The additional facts which my 

 observations establish, — particularly in relation to the recur- 

 rence of the phaenomenon on the same portion of the stalk 

 during several successive frosts, even after it had been cut off, 

 — appear to be irreconcileable with the idea that the physio- 

 logical functions of the plant have any share in the production 

 of it. We must therefore look to the moist earth for the large 



