COMPARISON OF THE SELANTHI WITH OTHER PLANTS. 
59 
and make the flower-grower a man of very general intelligence, 
without any labour on his part, and even without being aware 
of how he came by much of what he knows ; for it is the grand 
characteristic of the voluntary march of knowledge, that the 
distance is won without feeling any fatigue in the steps. 
Now, no plants can be better adapted for exciting and strength¬ 
ening this desire than the Selanthi. Of all vegetables they are 
the most singular in their appearance and habits ; and even the 
most zealous and profound botanists are yet in comparative igno¬ 
rance of their economy and uses in nature. Externally, they 
appear all flower, or all formed for the production of a flower; 
and they are always without leaves ; and some of the most splen¬ 
did of them have little or no development of root or stem. They 
grow, generally speaking, upon the roots of other plants,— 
often those of the ivy-tribe ; but though many of them adhere 
to the roots, or lower parts of plants, and some germinate under 
the epidermes, we cannot say that they are absolutely parasites, 
drawing their nourishment from these. Parasitism among plants 
is altogether an obscure subject, and one upon which the con¬ 
clusions at which we arrive by common observation are very 
liable to error. The fungi, for instance, stand accused of con¬ 
suming the substance, even the living substance, of those plants 
on which they appear. But this is only asserted, not demon¬ 
strated ; and the analogies are against its truth. From analogy, 
we are led to conclude that no one plant subsists, or can subsist, 
upon the living or undecayed substance of another. Sawdust 
cannot be used as the entire soil of every plant; neither is recent 
sawdust of the smallest value as a manure. Before the substance 
of one plant can conduce to the nourishment of another, there 
must be a decomposition different from simple mechanical divi¬ 
sion, however minute ; for the dust into which rotten wood can 
be crumbled" is of no more value as a manure than the sawdust 
of sound timber. Animals digest before they assimilate ; and, in 
so far as has been discovered, as plants have no digestive organs, 
the natural decomposition of substances appears to answer a simi¬ 
lar purpose in them to that which digestion answers in animals. 
So obscure is the subject, that though the favourite soil of many 
plants is known, we cannot name the specific food of any one 
individual. Probably it is gaseous in them all; and water or ain, 
according to the habit, is the vehicle in which it is administered. 
