THE STEM OF PLANTS. 21 
attraction which partly destroys the effect of gravitation, and 
determines the ascent of the liquid to a much higher level than it 
would attain in a larger tube. The phenomenon of capillarity is, 
then, added to the action of endosmose to favour the absorption of 
liquids by the radicular extremities. 
en the plant is furnished with leaves, there is a third force 
which unites with the two others in accelerating the absorption. 
The leaves are the seat of a considerable evaporation. The water 
dispersed into the atmosphere in the form of vapour leaves a 
partial vacuum in the vessels; this vacuum is immediately supplied 
by the afflux of the liquids flowing from the roots. In this 
manner leaf action is produced; this is a sort of suction which 
draws towards the leaves an afflux of liquid, which the radicular 
absorption is constantly compelled to supply. 
Thus endosmose, capillarity, and suction, in the upper part of 
the plant, are the physical forces which appear to play a part in 
the absorption carried on by roots. We must, besides, in order 
to explain the great phenomenon of the life of plants, bring in 
a foree very superior to all these physical actions. This is the 
action of vital force, that secret and invincible power which God 
only bestows and of which He alone directs the results. 
II.—Tue Srem or Puanrts. 
The stem is the axis of the ascending system of the vegetable. 
It is furnished at intervals with vital nodes, or eyes, from which 
spring the leaves, buds, and branches, arranged in a_ perfectly 
regular order. The root presents nothing of a similar nature. 
This characteristic enables us easily to distinguish in the vegetable 
axis between that which belongs to the stem, and that which is 
peculiar to the root. The stem is that part of the plant which, rising 
into the air, produces and supports the branches, boughs, leaves, 
and flowers. Through its tissues the liquids inhaled by the roots 
penetrate into the interior of the vegetable for the purpose of 
supplying it with nourishing juices, increasing its growth and 
maintaining its vital functions. 
, The form, size, and direction of the stem depend on the part 
