DAMAGE CAUSED BY PLANTS. "71 



in the way of water and inorganic nourishment from the latter, 

 whilst their supplies of organic nourishment is obtained by the 

 leaves from the air : these are the common mistletoe, and the 

 Loranthus or large misteltoe of the Oak. 



The common Mistletoe ( Viscum album), occurring on fruit trees, 

 as well as on many woodland species, as, for example, on Lime, 

 Poplar, Acacia, Scots Pine, and especially Silver Fir, but never (in 

 Germany) on Oak, Beech, Alder, Spruce, and there often forming 

 large bushes, with its greenish-yellow leaves persistent throughout 

 the winter, probably owes its wide extension and reproduction prin- 

 cipally to thrushes, which eagerly consume its white berries, and, in 

 cleansing their beaks from the very sticky flesh of the fruit, leave 

 a portion of it on the bark of the tree along with some of the seeds 

 contained in it. It does occur, though rarely, on Oak in Britain. 

 When the latter is smooth and without thick corky bark, a 

 rootlet of the germinating seed finds its way, under favourable 

 circumstances, into the woody-fibrous tissue, and forms the first 

 penetrating rootlet. This becomes overgrown and enclosed in the 

 new annual ring formed during the next year, but continues to 

 retain its direct connection with the plant flourishing outside 

 of the partially interruped cambial layer of the part of the tree 

 in question ; this first penetrating rootlet extends itself sidewards 

 in the same way into the young sapwood, annually forming new 

 penetrating rootlets near its point. These penetrating rootlets 

 have a long life, especially in the case of the smooth-barked 

 species of trees, become overgrown with a considerable number of 

 annual rings, and thus often extend into the wood to a depth of 

 4 inches ; when they die off, they rapidly undergo decomposition, 

 whereby the timber has the appearance of being bored through 

 with holes, and is thus rendered useless for technical purposes. On 

 branches, the portion above the swollen, crop-like excrescence 

 occasioned by the mistletoe, usually dies off after some time, pro- 

 bably in consequence of the withdrawal of the necessary supplies 



of water and mineral nutrients. 



The damage that can be occasioned in timber crops, especially 



' of Silver Fir, by the appearance of mistletoe in large quantities, is 

 at times not inconsiderable, especially when it is apt to show 

 itself on the stem, for it deforms the bole, and, as above explained, 



1 renders it useless as timber for technical purposes. There is, 

 however, no means of preventing the growth of mistletoe in 



