INJURIES INDUCED BY PLANTS 25 



parasitic. Its roots are partly attached to the roots of many 

 different plants, including several trees such as beech, hornbeam, 

 hazel, and alder. 



Notwithstanding traces of chlorophyll in the Orobanchacea, 

 these must undoubtedly be classed as true parasites, which derive 

 their nourishment exclusively from the host-plants to whose roots 

 they are attached. Of the numerous species, some occur so 

 plentifully on cultivated plants as to cause appreciable damage 

 e.g. Orobanche ramosa on tobacco and hemp, 0. lucorum on the 

 barberry and bramble, O. Hederce on ivy, O. rubens on lucerne, 

 and O. minor on red clover. The parasitism of the yellow bird's- 

 nest (Monotropa Hypopitys] is still doubtful, but, as its roots are 

 found in contact with those of conifers and the beech, it is 

 extremely probable that though most of its nourishment is got 

 from the humus a certain amount is also abstracted from these 

 plants. Besides Monotropa we have the Orchidacece that are 

 destitute of chlorophyll, which are all of a saprophytic nature. 



Nor can the Loranthacece be regarded as true parasites, 

 because for the most part they abstract only water and inorganic 

 food-materials from trees and shrubs, organic substances being 

 appropriated to a very limited extent. They possess leaves 

 containing chlorophyll, and behave towards their host in exactly 

 the same way as a scion does to a stock. In fact they yield up 

 a portion of the plastic substances which they themselves have 

 prepared to the host-plant, which employs them for its own growth. 

 Whether, however, this occurs in the case of all, or even most, 

 Loranthacecz is doubtful, but at all events such reciprocal nourish- 

 ing takes place with Loranthns europczus. The manner in which 

 the different species of this family abstract water and nourishment 

 by means of their roots from the plants which they inhabit varies 

 extremely, especially when the exotic species are taken into 

 account. 1 



The best-known species is Viscum album, the common mistletoe, 

 which is distributed throughout the whole of Europe, and Asia to 



1 See Solms Laubach in Pringsheim's Jahrbiichern f. wiss. Bat. VI., 

 pp. 575 et seq. R. Hartig, Zur Kenntniss von Loranthus europaeus und 

 Viscum attum,\vith a table, Zeitschrift fur Forst- u. Jagd-Wesen. 1876, 

 pp. 321 et seq. Dr. C. v. Tubeuf, Beitrdge ztir Kenntniss der Baumkrank- 

 heiten, pp. 9 28. Springer, Berlin, 1888. 



