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When the leaves are fully expanded, the great 

 determination of the sap is to these new organs. And 

 hence a tree which emits sap copiously from a wound 

 whilst the buds are opening, will no longer emit it in 

 summer when the leaves are perfect ; but in the varia- 

 ble weather, towards the ends of autumn, when the 

 leaves are falling, it will again possess the power of 

 bleeding in a very slight degree in the warmest days ; 

 but at no other times. 



In all these circumstances there is nothing analo- 

 gous to the irritable action of animal systems. 



In animal systems the heart and arteries are in 

 constant pulsation. Their functions are unceasingly 

 performed in all climates, and in all seasons ; in win- 

 ter, as well as in spring ; upon the arctic snows, and 

 under the tropical suns. They neither cease in the 

 periodical nocturnal sleep, common to most animals ; 

 nor in the long sleep of winter, peculiar to a few spe- 

 cies. The power is connected with animation, is lim- 

 ited to beings possessing the means of voluntary lo- 

 comotion ; it co-exists with the first appearance of 

 vitality ; it disappears only with the last spark of life. 



Vegetables may be truly said to be living systems, 

 in this sense, that they possess the means of convert- 

 ing the elements of common matter into organized 

 structures, both by assimilation and reproduction j but 

 we must not suffer ourselves to be deluded by the 

 very extensive application of the word life, to conceive 

 in the life of plants, any power similar to that produc- 

 ing the life of animals. In calling forth the vegetable 

 functions, common physical agents alone seem to 



