CH. IX.] DEATH AND DECOMPOSITION. 3'25 



•vvas but 6l.*25'^. The stamens of the ^Pompion, 

 Bignonia radiccms, and Polyanthus tuberosa have also 

 been observed to elevate the mercury at the time of 

 shedding their pollen, but in a much slighter degree. 

 In every instance this evolution of heat is occasioned 

 by a proportionate absorption of oxygen gas by the 

 stamens and pistils at the instant of fecundation. 

 The stamens oHhe Aru7nma€ulatum, forinstance, have 

 been shewn by M. Saussure to absorb at that time 

 '200 times their bulk of oxygen gas, converting it 

 into carbonic acid. But, although some plants thus 

 cause a great extrication of heat, and others are 

 capable of resisting the greatest Imown cold to ^vliich 

 they can be exposed, yet all have degrees of tem- 

 perature most congenial to them, and if subjected to 

 lower temperatures are less or more injured propor- 

 tionately to the intensity of that reduction. If the 

 reduction of temperature be only slightly below that 

 which is congenial, it only causes the growth of the 

 plant to diminish, and its colour to become more 

 pale ; this effect being now produced by the plant "s 

 torpidity or want of excitement to perform the 

 requisite elaboration of the sap, as it is by over 

 excitement when made to vegetate in a temperature 

 vrhich is too elevated. If blossoms are produced at 

 all, they are unfertile, and the entire aspect of the 

 plant betrays that its secretions are not healthy, and 

 its functions are deadened. Mr. Knight says, that 



