AND CONSEQUENTLY COLD. 187 



refuse to convey their fluid, bo that the blossoms of fruit-trees 

 in a north-east wind, while they are robhed of their fluid con- 

 tents by evaporation, can get no assistance from the roots 

 through the stem, and necessarily perish; and this is no 

 doubt one reason why open standard trees cast their flowers 

 under a low temperature during the cold dry winds of our 

 springs. 



I have now before me a standard "WasHngton Plum, bearing a crop 

 of fruit in a garden where nearly everything else lost its blossoms on the 

 24th of April, 1854, when the thermometer fell to 18° Fahr. In this 

 case a pile of firewood had been heaped round the stem to the height of 

 the branches, and thus effectually guarded it from cold, Probably 

 something was also owing to the warmth radiated from the pile of 

 wood. This, however, only belongs to a class of facts of which the 

 Magnolia grandiflora is an instance. Formerly there were trees of this 

 species in Paris, whose only protection in winter was a heap of dry 

 straw piled over their roots, so as entirely to cover them, and thatched 

 to the height of five or six feet, so that the head of the trees formed the 

 apex of a cone, the base of which was straw. By this precaution the 

 earth is unable to freeze, and the fluids in the interior of the tree are 

 maintained at a temperature approaching to that of the earth. "While, 

 on the other hand, if the earth is frozen hard, the fluids in the roots 

 are frozen also, and they thus tend to lower the temperature of the 

 fluids and the branches. But this is, perhaps, not the only reason why 

 tender trees are preserved by this sort of protection. It is to be 

 observed that the destructive effects of frost are in proportion to the 

 succulence of the parts on which it acts ; and it may be, that the con- 

 tracting influence of cold gradually forces the fluids out of the unpro- 

 tected branches into those lower parts which are guarded from the 

 action of cold. Then the branches being pro tanto emptied of fluid, or 

 dried, are thus deprived of a part of their susceptibility to cold. 



It has been objected by a critic that there is no experimental proof of 

 contraction of tissue taking place under the influence of cold. But if the 

 reader wiU turn to Biot's curious and little known observations, briefly 

 reported in Senslow's Botany, p. 205, he wiU find that contraction imder 

 cold has received the most conclusive experimental proof at the hands of 

 one of the best of modern observers. There is also a fact on record which 

 has hitherto remained without explanation, but which was probably con- 

 nected with the contracting power of cold. In the winter of 1838, when 

 the thermometer feU to 2° Fahr., Mr. Rogers observed the following 

 phenomena : — During the extreme cold the branches of a Lime-tree, 

 which overhung a part of his garden, drooped so as completely to lie 

 upon the ground, and those above fell proportionately. The branches 



