20 



radicle from the seed would not penetrate. Thirdly, if one of the yet unbroken 

 protuberances be traced down by means of thin horizontal sections, it is found 

 that the portion under the bark is, in many instances, for some distance irregular 

 in shape, exhibiting such an appearance as might be expected in cutting through 

 a mass of tissue parallel to the bark. 



The proof of a decided connexion between two plants of Mistletoe on the 

 same branch has not yet been found ; and this is not to be wondered at, when we 

 consider how small such a connexion may be. 



Mode of Growth of a Plant on the Tree. — A transverse section of Mistletoe 

 on a branch usually shows a central root and one or more side roots, all of 

 which are generally directed towards the central pith. A curious deviation 

 from this was seen in the case of a plant which had grown in the angle between 

 two branches. The central root was directed between the centres. 



The explanation of such a section as that which is represented at fig. 7 is 

 this — the radicle after having penetrated the bark and cambial layer, from which 

 it derives the greater part of its nutriment, gradually advances through the albur- 

 num, then pushes its way through the mature wood towards the central pith. This 

 is proved to be the case by the fact that we find roots actually penetrating to the 

 pith, in one case even the point of the radicle just missed the centre of the pith 

 and had passed it ; and we must allow the twig or branch to have at least one 

 ring of wood before the deposit of the seed, or the advance of the rkizome. 

 "While the root is thus advancing towards the pith, the Mistletoe expands 

 laterally in the liber of the branch, where an additional growth is provoked, so 

 to speak, by the irritation of the parasite. This additional secretion of new 

 wood is so great as to cause the central pith to become eccentric. 



The lateral expansion of the Mistletoe causes a sort of corm or crown of 

 the root to appear, which continues to expand in all directions, following the 

 curvature of the branch. At certain points it sends down additional roots, 

 which penetrate the wood in the same way as the original root. In this way the 

 roots on either side of the central one, in a transverse section, and the numerous 

 wedged-shaped ones, in a longitudinal section, are accounted for. This lateral 

 expansion, in some cases, goes on until the branch is almost entirely surrounded 

 by a ring of Mistletoe, with its roots converging towards the centre, like so many 

 spokes of a wheel. Thus the Mistletoe carries it3 own death with it, for, by 

 living, it deprives itself of the "means by which it lives." 



In some cases this lateral expansion, instead of pushing the bark up 

 before it, encloses it. Fig. 7 (a) shews a portion of bark enclosed between two 

 roots, but fig. 8 is worthy of especial notice, for by it the penetrating power of 

 the roots is undeniably proved. The section is one of an apple branch, which 

 was itself exhibited at the last meeting of the club. It is a quarter of an inch 

 in diameter. The bark enclosed is of the same date as the bark of the branch, 

 and forms a continuation of it, beyond the root of the Mistletoe, which has 

 enclosed it. The enclosed portion of the bark (a. fig. 8) shews the masses of 



