On the Reproduction of Buds. 77 



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 con- 

 sists of four distinct substances, the epidermis, the true 

 skin, the bark, and its internal substance, which from its 

 mode of formation and subsequent office I have supposed 

 to be alburnous : there is also in the young tubes a transoa- 

 rent line through the centre, 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 alburnous substance, and 

 therefore this, with the preceding facts, is adduced to prove 

 only that the reproduced buds of these plants are not gene- 

 rated by the cortical substance of the root : and I shall 

 proceed to relate some experiments on the apple, and 

 pear, and plum 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 cutoff about an inch below the points whore 

 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 and light. Tn the beginning of April I 

 observed many small elevated points on the bark of these 

 roots, and, removing the whole of the cortical substance, I 

 found that the elevations were occasioned by small protube- 

 rances on the surface of the alburnum. As the spring ad- 

 vanced, many minute red points appeared to perforate the 

 baik : these soon assumed the character of buds, and pro- 

 duced shoots in every respect similar to those which would 

 have sprung from the organized buds of the preceding year. 

 Whether the buds thus reproduced derived any portion of 



their 



