The vegetable SYSTEM. 
■9 
ed at the heighth to which it was carried ; and it dies to the ground. 
The Root requires a lefs degree of warmth to keep it in a l1;ate of 
potential life ; therefore the fmall remains of Heat that are under 
the furface in Winter preferve this : but in extreme froft it alfo 
decays ; the Juices are reduced to ice, and the Root no more 
recovers. This is the effect of Winter upon the generality of our 
Plants. Annuals requiring more heat than perennials, perifli Root 
and all, at the approach of the cold j and 'Trees by the hard mat- 
ter of their trunks defend the inclofed Juices : thefe are not con- 
tradid:ions of the general law ; but natural exceptions. 
The warmth of Spring begins again to roufe the Ragnant Juicea 
of perennial Roots, and call them upwards : at the fame time the 
earth, the Plants certain food, is moiftened and didblved by the 
rains of that Seafon ; therefore it is in the juR condition to afford 
a full fupply. Thus the vegetable extends, and is encreafed, and 
grows, through this time, and the fucceeding Summer ; till the 
chill Autumn Rops its progrefs ; if it have not before been termi- 
nated by frudlification. According to the Rronger or weaker texture 
of its parts it either dies entire, as in the annual kind; or what is 
under ground remains, as in perennials j or its trunk and branches 
firm, though naked, preferve themfelves through Winter, as Roots 
above the ground; lofing only the tenderer parts, their Leaves; not 
always thofe. 
CHAP. VI. 
Of the Rise and Fall of the Sap. 
W E have feen that it is heat which principally occafions the 
Rife of the Juices in vegetables : and therefore this afeent is 
greateR in the hotteR feafons. In Plants it is only in thofe feafoir 
that it takes place ; but in trees whole firmnefs preferves them above 
ground, there is fome rife of the Sap at all times, even in the depth 
of winter. Reafon declares this, and what we fee confirms it. The 
branch of a Vine which grows in the open air, near a Rove, being 
VoL. II. D Itt 
