240 Of the Roots of Plants. 
fores in the roots than in the ftalks ; therefore in thd 
plantule we may conceive a point of feparation ; fuch, 
that all one fide of the root fhall be unfolded by the 
groffer j uices, and all the other fide by the more fubtile 
ones. 
If now the plantule be inverted when its parts begin 
to unfold, the juices which enter the root being ooarfeft, 
when they have enlarged the pores to admit juices of a 
determinate weight, thofe juices preffing the root more 
and more, will drive it downwards, and this the more as 
the root is more extended or enlarged; for the point of 
feparation, being conceived as the fix’d point of a lever, 
they will adt by the longer arm. At the fame time the 
volatile juices having penetrated the ftalk, will tend to 
give a diredtion from below upwards, and by reafon of 
the lever, will give it more and more every day till it be 
perfedtly eredt. 
Mr. Aftruc accounts for perpendicularity of the Items, 
and theii redrefiing themfelves on thefe two principles. 
Firft, that the nutritious juice arifes from the circum¬ 
ference of the plant, and terminates in the pith. Second, 
that fluids contain’d in tubes, either parallel or oblique to 
the horizon, gravitate on the lower part of the tubes, 
and not at all on the upper. 
Whence it eafily follows, that in a plant pofited either 
obliquely or parallel to the horizon, the nutritious juice 
will adt more on the lower part of the canals than on the 
upper; and by this means infmuate more into the canals 
communicating therewith, and be colledted more copi- 
oufly therein; thus the parts on the lower fide will receive 
more accretion, and be more nourifhed than thofe on the 
upper ^ the coufequences whereof muit be, that the ex¬ 
tremity of the plant will be obliged to bend upwards. 
The 
