FALL OF THE LEAF. 363 



are naturally green, we find that in proportion to the health of the 

 plant the green is darker ; and when not healthy, it is more of the 

 yellow cast. Those that are naturally yellow do not change : yellow is 

 more or less the colour that green vegetables take on in the act of dying. 

 Therefore when plants are not of so dark a green as common, they 

 have but few or little powers of life. A dark green in any plant shows 

 great vigour of life, and the growth is luxuriant. 



Of the Leaves. — Some plants throw out their leaves much earlier than 

 others. 



Query. Are those plants of colder climates, because they can vege- 

 tate with less heat than those of warmer climates ? and, conversely, of 

 vegetables of warmer climates, as they require more heat, are they, in 

 some degree, kept back in putting forth their leaves ? If so, then we 

 might judge of the warmth originally suitable to a vegetable by the 

 comparative times of their throwing out their leaves and flowers. 



We sometimes find trees throwing out leaves, and even blossoms, 

 about the beginning of October: such I have observed have dropped 

 their leaves very early in the autumn, so that they had gone through 

 their suspension of action a sufficient length of time to take on a new 

 action. But such late growths are commonly, if not always, weaker 

 than those in due season; the leaves are paler, commonly with a 

 mixture of yellow, which denotes weakness. 



I had a Lime-tree that threw off its leaves in August ; I thought 

 it was dead, but it threw out a second set of leaves in the latter end of 

 September ; but they were pale, therefore not healthy or vigorous. A 

 Horse-chestnut tree at the King's Head door, Brompton, had one of its 

 branches which lost its leaves very early in the season, and by the 

 latter end of September it had shot out fresh leaves and a full-grown 

 flower : the leaves were paler than those in due season. 



Leaves have considerable motion when the wind blows. Is this in 

 some degree to take off the force of the wind upon the whole tree ? 



Some trees, as the Birch, Poplar, have much smaller branches than 

 others, the stem being the principal part ; such also have small leaves ; 

 of course those that have large branches having larger leaves. 



Of the Casting of the Leaves of Vegetables. 



Every vegetable is deciduous, but differs in regard to times, and pro- 

 bably may be divided into the following : — 



The first is what may be called annual, being similar to those plants 

 which die the same 'year or the same season, or rather when finished 

 growing, as in all the plants commonly called deciduous ; but to keep 

 to the true analogy, they should be called , as it is 



