By Professor Lindley. 



301 



Professor Morrex's observations were made upon various plants 

 frozen in the spring of the present year, having been exposed to a 

 temperature of — 4° to + 9° Fahrenheit. One of his statements I 

 give in his own words. " In the parenchyma of many plants, and 

 especially in that of succulent fruits, it is easy to ascertain what 

 modifications are caused by frost in the internal organs of plants. 

 If a frozen apple is opened, it is obvious that the ice is not a conti- 

 nuous mass, but that it is a collection of a multitude of little 

 microscopical icicles. Under the microscope, the fact becomes 

 evident. We know how excessively hard some fruits become when 

 frozen by this mosaic of icicles, especially pears. If we thaw them 

 it is seen that on the instant a multitude of air-bubbles are extri- 

 cated from the juice of the fruit, and that this juice has then 

 acquired new chemical qualities. I wished to ascertain the cause 

 of these phenomena, and the following is what observation has 

 shewn me. I studied for this purpose more particularly the tissue 

 of the apple. Each cell is filled with a small icicle which has 

 in its middle a bubble of air. We know, that when water freezes 

 the crystals so arrange themselves, that the air separated from their 

 mass by the solidification of the liquid is intercalated between their 

 planes. This air also places itself in a mass of congealed water in 

 a regular manner, the nature of which depends entirely upon that 

 assumed by the crystals, as may be seen by freezing water in a cylin- 

 drical vessel, when the air-bubbles always assume the form of a very 

 long cone, terminated by a spherical cap. The augmentation of the 

 volume of water is in great measure owing to this interposition of 

 masses of air. All these effects take place in each cell of a frozen 

 apple, which thus increases in size because each cell of its tissue 

 becomes individually larger. When thawed, the cell recovers 

 itself by the elasticity of its vegetable membrane, and frozen fruit 

 becomes, as we know, very much shrivelled. Each cell, therefore, 

 acts like a bottle of frozen water, only there is no bursting, because 

 the membrane is extensible." 



VOL. II. 2nd series. 2 R 



