APPENDAGES OF THE STEM. 155 



heat, whence they derive colour, and their juices 

 motion ; the latter become subtilised and evapo- 

 rable, and as, they fly off, leave them insatiate for 

 fresh supplies. This agency of the foliage, there- 

 fore, gives an impetus to every current in the 

 system, and consequently must have a powerful 

 effect in advancing the amplification of the plant. 



To the agency of the leaves have been ascribed 

 the fruitfulness of trees, and the more perfect matu- 

 ration of the tubers of herbaceous plants. Both bulbs 

 and tubers, it is said, being more or less enlarged 

 according as the leaves are able to " throw down " 

 ample supplies of elaborated sap. Now, although it 

 be unquestionable that the leaves are recipients of 

 divers atmospheric principles and influences neces- 

 sary to the plant, and their amplitude and vigour 

 are proof of their powers for that purpose ; yet we 

 find on examination, that the rule js not universally 

 true, that bulbs and tubers are large in proportion to 

 their system of foliage. We may only instance the 

 most leafy individuals in a field of turnips, carrots, 

 parsneps, &c., which are always found to have com- 

 paratively smaller tubers than the less leafy portion 

 of the crop. We may also remark the disparity of 

 the tubers and foliage of the short-top radish, as 

 further proof that tubers are not always in size pro- 

 portioned to their quantity of leaves. Moreover, 

 we may repeat, that both bulbs and tubers are occa- 

 sionally produced without the assistance of leaves. 



Stipulce. This name is given by botanists to a 



