204 CONVERSION OF THE ASCENDING SAP. MISSELTOE. 



319. Although the peculiar characters of the proper juices of 

 the tree are thus communicated to the ascending sap, yet they 

 are possessed by it in but a very slight degree ; and it is in con- 

 sequence of this, that the ascending sap of all trees possesses very 

 nearly the same properties ; as is shown by more than one 

 curious fact. There are some plants which have not the power 

 of forming true roots for themselves, and which obtain their sup- 

 ply of sap from the stems of trees to which they attach them- 

 selves. Such is the common Misseltoe. The seeds of this plant 

 are deposited by birds on the exterior of the stems and branches 

 of trees ; and the root-fibres which they put out, insinuate them- 

 selves through the crevices of the bark, and incorporate them- 

 selves with the wood. 



320. Now the Misseltoe imbibes the ascending sap from the 

 wood of the tree or stock on which it grows ; and this it converts 

 into a proper juice, adapted to nourish its own structure, by 

 means of its own leaves. The ascending sap of most trees being 

 nearly alike, the Misseltoe seems to grow with almost equal faci- 

 lity on a great variety. It is remarkable, however, that it is 

 very rare on the oak ; and it is perhaps this circumstance which 

 caused the plant, when found in connection with that tree, to be 

 regarded by the ancient Druids in a religious light. Perhaps it 

 is the tannin produced by the oak, of which a small portion 

 will be contained in the ascending sap, and which has been 

 already spoken of as exerting a prejudicial influence on the vege- 

 tation of most other species (. 209), which is unfavourable to 

 the growth also of the Misseltoe. 



321. Now it is a very curious fact, that the law of growth 

 of these root-fibres is different from that which governs other 

 roots. For whilst the latter grow downwards towards the centre 

 of the earth, these grow towards the centre of the bough or stem 

 into which they may be penetrating. This tendency was ascer- 

 tained by the experiments of the French physiologist Dutrochet, 

 who caused a seed of Misseltoe to germinate, when hung by a 

 thread near a large ball of metal ; and he found that the radicle 

 always directed itself towards the centre of this ball, near what- 

 ever part of the surface it might be placed. By this curious 



