EFFECTS OF FROST ON TREES. 



4. The action of freezing affects each in- 

 dividual organ in such a manner that there 

 are as many separate pieces of ice as there 

 are aquiferous organs. Every one of these 

 organs thence undergoes a dilatation which, 

 in the mean time, never proceeds to the 

 extent of fracture. 



5. This dilatation depends, in a great 

 measure, on the separation of air contained 

 in the water. Thus, frozen water, which 

 burst an iron cannon of a finger's thick- 

 ness, according to the experience of Biot, 

 and shattered the copper globe of the philo- 

 sophers of Florence, by a force of 27,720 

 pounds, produces no fracture of a vegetable 

 cell, formed by a membrane of immeasura- 

 ble delicacy. 



6. The system of Dr. Hauy, which main- 

 tains that water, in a state of congelation, 

 kills plants, because it compresses their col- 

 lars and attacks their roots, ought to be rej ect- 

 ed ; also his hypothesis that, during freezing, 

 the fibres are contracted, and the organs 

 rent by the dilatation of the sap, 



7. It is to be inferred, since the sap, pro- 

 per juice, fluid of the cells, and, finally, all 

 the menstrua which are found in the organs 

 of plants, are not formed of pure and liquid 

 water, that vegetables, on that account, resist 

 congelation within certain limits, as the ex- 

 periments of Blagden have demonstrated 

 that the materials v\'hich affect the purity of 

 the water, allow the liquid to attain uncon- 

 gealed, a degree of cold otherwise sufficient 

 to freeze it. 



8. The extrication of air from water dur- 

 ing the process of freezing, exerts the most 

 hurtful influence on the life of plants ; it 

 introduces air into organs which are not de- 

 signed to elaborate it ; and this separation 

 of air is the first advance toward the de- 

 composition of the sap and the materials it 

 precipitates, so that during a thaw a chemi- 

 cal action begins by killing the plant. 



9, The distention, thus developed by the 

 contents of the cells and aquiferous organs, 

 eliminates the air on thawing, and, because 

 the air is not controlled by the liquid, throws 

 a large quantity of the latter into the air 

 cavities and vessels ; so that the apparatus 

 designed to contain liquids, contains water 

 and air, while that naturally intended as a 

 vehicle for air conveys water. The physi- 

 ological relations are changed, and the or- 

 ganization cannot sustain such mutations 

 with impunity. 



10. Thus, if frozen plants be not depriv- 

 ed of life, by the decomposition of their 

 juices, the loss of excitability or chemical 

 disturbance of all their parts, they are de- 

 stroyed by the perversion alone of their 

 functions. 



[We publish the foregoing as an interest- 

 ing contribution to this obscure part of ve- 

 getable physiology, to which the French 

 and Germans have paid more attention than 

 the English. In this country, where cer- 

 tain disastrous forms of winter-blight are 

 prevalent among fruit trees, the whole na- 

 ture and eflfects of congelation become high- 

 ly interesting. 



There appear to us, however, to be objec- 

 tions to some of M. Morren's aphorisms, 

 which we are able, at the present moment, 

 only to indicate, with the hope of returning 

 to the subject more fully hereafter. 



In the first place, the usual opinion that 

 the injurious effects of freezing on trees is 

 a mechanical one, bursting the sap-vessels, 

 etc., owes its weight to every-day observa- 

 tions. Everyone familiar with country life 

 in the Northern States, knows, for instance, 

 that severe cold has the effect occasionally 

 of rending the entire trunks of large trees 

 with a loud noise like the report of a can- 

 non. It scarcely seems possible that this 

 could take place without also " rending the 

 organs" of the trees. 



