a 
T H e V E G E 'r A B L E SYSTEM. 
ihoiild be produced there ; and we fee this in Eift : the hotteft 
countries affording in general the tailed: trees, the largell flowers, 
and the flnefl; fruits. ^ 
The power of Heat is fo great on plants, that an excefs or defici- 
ence of it in any coniiderable degree, is equally fatal. That which was 
natural to them in their own foil fupports them alfo in our iloves : 
but more or lefs changes their time of duration, and equally deflroys 
them, tliough by different means. 
A 
Perenniae. Plants of fomewhat warmer climates become annual 
in thofe a little colder. The earth wants Heat in Winter to keep 
up the primary circulation which is in the Flefh of the root j and it 
decajs: but Seeds being ripened firfl:, the Vegetable may be raifed 
in Spring and live the Summer. Many of thofe whofe woody Stems 
naturally remain throughout the year, when they are brought where 
there is lefs Pleat, lofe them in Winter; but the Root, being har- 
dier, lives. Thus weak Shrubs of warmer climates are reduced to 
the condition of perennial Plants in thofe which are fomewhat cold- 
er ; and perennial Plants to annual. This change is in many in- 
flances reciprocal : Plants which are annual here, living through 
Winter, in more fouthern countries ; and thofe which lofe their 
Stalks retaining them there throughout all Seafons. 
That Heat is thus effential to Vegetation, and thus appropriated 
in the degree to Plants, according to their native place, we fee by 
the efledfs of an inconfiderate encreafe or diminution. The more 
Heat a Plant receives the thinner are its Juices, the fwifter they 
move, and thefafter it grows : therefore if we give any Species much 
more than its natural proportion it becomes luxuriant ; but nature 
will not be forced thus with fafety : it fades foon after ; and pe- 
rifhes inevitably. On the contrary, if we allow lefs than the natu- 
ral Heat, in any important degree, the Plant, though it continues to 
live, ceafes gowing ; it produces no Flowers or Fruit; and if the 
warmth be (fill fomething more decreafed, it lofes the Leaves, and 
dies abfolutely. 
Thus 
