PARASITISM IN FLOWERING PLANTS. 
229 
leaf- organs. On the other hand there is usually a great develop- 
ment of the inflorescence. Parasites seem, and sometimes are, 
all flower, and their flowers are generally handsome. The largest 
flower known is RafflesiaArnoldi, a parasite on vines in Sumatra, 
and a profusion of blossom is produced by our more familiar 
Dodders and Broomrapes. 
The meaning of these modifications in the structure of para- 
sites is in part obvious. Organs for the acquirement of raw food 
are clearly not needed ; all that is required is a union of the tis- 
sues of the parasite and nurse-plant so close that the fluid nutri- 
ment of the latter may readily pass from one individual to the 
other. Nor, as this pabulum is already in a somewhat thickened 
condition, is an extensive surface for evaporation needed. The 
usual absence of chlorophyll is less readily explained. It is 
commonly stated that the food of the parasite is already in a 
prepared state, and that therefore no elaboration on its part is 
necessary ; but a very little examination is sufficient to show 
that this is not the case. A very large number of parasites 
possess an abundance of green colouring matter, and there is no 
reason to suppose it useless to them. But a more direct argu- 
ment is found in the fact, that the juices of stock and parasite 
have usually an entirely different chemical composition. It 
must, indeed, be evident that a parasite, such as the Dodder, 
which often holds in its strangling embraces half-a-dozen or 
more different plants of various composition, must have the 
power of selecting what it needs from each ; and when we find 
compounds in the parasite which do not occur in any of its 
victims, we are forced to allow that processes of assimilation go 
on in its tissues. The chemistry of these plants has been but 
little studied ; they, however, contain stores of starch, and are 
generally far richer in hydrocarbonaceous principles than the 
species upon which they grow. Thus Orobanches and Cytinus 
contain abundance of oleo-resinous matter, and a species of 
Balanophora is said to be employed in Java to make candles. 
This excess of hydrocarbons is especially worth remark, as it 
exists along with a loss of large quantities of carbon by the 
constant expiration of carbon-dioxide, for in relation to the at- 
mosphere parasites act like the coloured parts of other plants. 
Nearly all of them possess stomata, but in smaller numbers than 
foliage-bearing vegetables. Many contain strongly astringent 
principles, and most become black when dried. 
We must then admit that the power of elaboration of new 
substances is possessed by parasites, and it seems likely that 
along with the constant expiration of carbon-dioxide, there is 
concurrently an absorption of the same gas in smaller quantity 
continually going on in the ordinary way ; the amount of car- 
bon-dioxide apparently given out would then in reality only 
