Oh the Origin and Formation of Roots. 35 



« former memoir, that if the mould be taken away, so that 

 the parts of the larger roots, wUich adjoin the trunk, be ex- 

 posed to the air, such parts are subsequently found to con- 

 tarn much heart wood*. 



I would wish the preceding observations to be considered 

 as extending to trees only, and exclusive of the palm tribe - 

 but I believe they are nevertheless generally applicable to 

 perennial herbaceous plants, and that the buds and fibrous 

 roots of these originate from substances which correspond 

 w.th the alburnum and bark of trees. It is obvious, that 

 the roots which bulbs emit in the spring, are generated by 

 the sap which descends from the bulb, when that retains its 

 natural position ; and such tuberous-rooted plants as the po- 

 tatoe offer rather a seeming than a real obstacle to the hypo- 

 thesis I am endeavouring to establish. The buds of thesfc 

 are generally formed beneath the soil j but I have shown, i,i 

 a forrner memoir, that the buds on every part of the stem 

 may be made to generate tubers, which are similar to those 

 usually formed beneath the soil; and I have subsequently 

 seen, m many mstances, such emitted by a reproduced bud 

 without the calyx of a blossom, which had failed to produce 

 fruit ; but I have never, under any circumstances, been able 

 to obtain tubers from the fibrous roots of the plant. 



The tube therefore appears to differ little from a branch' 

 which has dilated instead of extending itself; except that it 

 becomes capable of retaining life during a longer period - 

 and when I have laboured through a whole summer to coun- 

 teract the natural habits of the plant, a profusicm of blos- 

 soms has in many instances sprung from the buds of a tuber 

 The runners also, which,' according to the natural habit 

 o\ the plant, give existence to the tubers beneath the soil, 

 are very similar in organization to the stem of the niant, and 

 readily emit leaves, and become converted into perfect stems 

 in a few days, if the current of ascending sap be diverted 

 into them ; and the mode in which the tuber is formed above 

 and beneath the soil is precisely the same. And when the 

 sap, which has been deposited at rest during the autumn and 



• PJiiIo:ophicaI Transactions for 1?01 

 C2 



Winter. 



