288 Mr. Knight’s Account of some Experiments 
one or two, and the bark between them, as in the former expe- 
riments, was removed, no wood was generated by the insulated 
bark. 
I shall conclude my Paper with a few remarks on the forma- 
tion of buds, in tuberous rooted plants, beneath the ground. 
They must, if my theory be well founded, be formed of matter 
which has descended from the leaves through the bark. I shall 
coniine my observations to the potatoe. Having raised some 
plants of this kind in a situation well adapted to my purpose, I 
waited till the tubers were about half grown ; and I then com- 
menced rny experiment by carefully intersecting, with a sharp 
knife, the runners which connect the tubers with the parent 
plant, and immersing each end of the runners, thus intersected, 
in a decoction of logwood. At the end of twenty-four hours, I 
examined the state of the experiment; and I found that the de- 
coction had passed along the runners in each direction ; but I 
could not discover that it had entered any of the vessels of the 
parent plant. This result I had anticipated; because I concluded, 
that the matter by which the growing tuber is fed, must descend 
from the leaves through the bark ; and experience had long 
before taught me, that the bark would not absorb coloured in- 
fusions. I now endeavoured to trace the progress of the infusion 
in the opposite direction ; and my success here much exceeded 
my hopes. 
A section of the potatoe presents four distinct substances : 
the internal part, which, from the mode of its formation and 
subsequent office, I conceive to be allied to the alburnum of 
ligneous plants ; the bark which surrounds this substance ; the 
true skin of the plant; and the epidermis. Making transverse 
sections of the tubers which had been the subjects of the 
