CLASSIFICATION OF PARASITES. 159 



4. ABSORPTION OF NUTRIMENT BY PARASITIC PLANTS. 



Classification of parasites. — Bacteria. — Fungi. — Twining parasites. — Green-leaved parasites. — Tooth- 

 wort.— Broom-rapes, Balanophorese and EafHesiacese. — Mistletoe and Lorauthus. — Grafting and 

 budding. 



CLASSIFICATION OF PARASITES. 



The ancients understood by parasites people who intruded uninvited into the 

 houses of the rich in order to obtain a free meal. The designation was first applied 

 to plants by an eighteenth - century botanist, named Micheli, in his work " De 

 Orobanche" (1720) wherein are described amongst others, many kinds of "plantae 

 secundaria aut parasiticae". Micheli included under this term plants which with- 

 draw organic compounds from living plants or animals, thus sparing themselves the 

 labour of forming those compounds out of water, salts, and constituents of the air. 

 For a long time all epiphytes, including mosses and lichens growing on the bark of 

 trees, and indeed even many climbing plants, were held to be parasites. Thus, it is not 

 long ago that Clusia rosea, which occurs in the Antilles, was described as a regular 

 vampire, in whose embraces other plants met their death; and it has been asserted 

 respecting a whole series of other plants of the tropical zone, including, for instance, 

 several species of fig, that they attach their stems and branches to other trees, 

 divest themselves of their bark, and cause the death of that of the neighbour 

 attacked as a consequence of the pressure which they exert. The young wood of 

 the invader would then come into direct connection with the young wood of the 

 plant assailed, and the possibility would thus be afforded of draining the latter of 

 all its juices. 



These assumptions, at least as regards the exhaustion of juices, have not been 

 confirmed. When individuals of species of Clusia or Ficus, which have roots buried 

 in the earth, and are themselves already grown up into stately leaf -bearing plants, 

 attach their flattened stems and branches to other plants, investing them so 

 completely as to interfere with the process of respiration, this constitutes, at all 

 events, an invasion of one of the most important of the vital functions of the plant 

 attacked, and may ultimately cause its death; but the killing is not under these 

 circumstances due to drainage of juices, but is brought about by suffocation. 

 Lichens, too, when they cover the bark of trees with a close-fitting mantle, may 

 possibly restrict the process of respiration through particular parts of the cortex, 

 and thereby injure the development of the tree in question; but they are not on 

 that account to be looked upon as parasites any more than the fructifications of the 

 species of Telephora, and other Basidiomycetes, which grow up rapidly from the 

 ground, and, spreading out like plastic doughy masses, envelop all objects which 

 come in their way, and ultimately stifle such as are living, namely, grass haulms, 

 bilberry bushes, &c. Even creepers, which impose woody stems upon the trunks of 

 young trees, winding round them like serpents, and restricting their circumferential 

 growth at the parts in contact with the coils, so that ultimately the latter lie 



