UNION OF DIFFERENT SPECIES OF PLANTS. 
253 
In green-houses we often see an assemblage of the different 
species of the Cereus all stuck upon the Speciosissima , or upon the 
Pereslua. This inoculation of one species with another is easily 
performed : the little branch intended to be inserted is reduced 
at the bottom, so as to fit a hole made in the stock, in which, when 
placed, it readily adheres, by reason of the glutinous consistence 
of the respective juices ; and henceforth unites with and draws 
support from the foster stem on which it is inserted. Some of 
these associate very well; especially when the dwarf growers are 
elevated on the stems of the taller sorts ; but at best they are only 
practical whims or curiosities. 
Parasitical plants are those which breed and live upon other 
plants. The far greater number of these belong to the mosses, 
lichens, and fungi. Some of these use the stems of trees and 
other plants as supports or habitations only. Others attach them¬ 
selves to the leaves, culms, or roots of healthy plants, subsisting 
on the sap and destroying the organization. Of these last the 
mildew on trees and the rust on corn are well known. Parasites 
of more conspicuous character are the toothwort, the broomrape, 
and the mistletoe : these seat themselves upon or under the bark, 
sucking the juices by an inflated base firmly fixed on the alburnum 
of the tree on which the parasite grows. The Dodder is another 
curious plant, being only supported by its own roots until its 
twining stems can lay hold of the stems of some other plant, on 
which it afterwards subsists. In warmer climates the beautiful 
Loranthus, which invariably inhabits the oak, is a parasite ; and is 
said to have been the mistletoe of the Druids, and on this account 
must have once been common in England, but extirpated along 
with its devotees. It is rather strange that this highly ornamental 
plant has not lately been introduced into this country, as the 
mistletoe has been into Scotland; that is, by removing a young 
oak on which it grows naturally, or by grafting or budding it 
upon a young oak in a pot. 
But notwithstanding the very intimate union which some of the 
last mentioned plants form with those on which they grow, there 
is no perfect inosculation of their membranes, as already observed, 
so as to alter either their flowers or fruit. It is said, indeed, that 
pears worked on the quince stock are more austere than they are 
on their own stock; but this has never been clearly proved. 
There are some instances of moderately or weakly growing stocks 
