»59 
Mr. Knight on the Reproduction of Buds. 
the surfaces made by the knife in dividing the roots into 
cuttings ; and the buds of these, in many instances, elongated 
into runners which gave existence to other tubers, some of 
which I had the pleasure to send to you. 
I have in a former Paper remarked, that the potatoe consists 
6f four distinct substances, the epidermis, the true skin, the 
bark, and its internal substance, which from its mode of forma- 
tion, and subsequent office, 1 have supposed to be alburnous : 
there is also in the young tubes a transparent line through the 
center, which is probably its medulla. The buds and runners 
sprang from the substance which I conceive to be the alburnum 
of the root, and neither from the central part of it, nor from 
the surface in contact with the bark. It must, however, be 
admitted, that the internal substance of the potatoe corresponds 
more nearly with our ideas of a medullary than of an albur- 
nous substance, and therefore this, with the preceding facts, is 
adduced to prove only that the reproduced buds of these 
plants are not generated by the cortical substance of the root : 
and I shall proceed to relate some experiments on the apple, 
and pear, and plumb-tree, which I conceive to prove that the 
reproduced buds of those plants do not spring from the 
medulla. 
Having raised from seeds a very considerable number of 
plants of each of these species in 1802, I partly disengaged 
them from the soil in the autumn, by digging round each 
plant, which was then raised about two inches above its former 
level. A part of the mould was then removed, and the plants 
were cut off about an inch below the points where the seed- 
leaves formerly grew ; and a portion of the root, about an inch 
long, without any bud upon it, remained exposed to the air 
LI 2 
