Plants -- Identification; Wild flowers -- Great Britain
The Dodder now grows rapidly, giving off branches which search in all
directions for additional supports, sometimes climbing from one plant to
another, and producing new suckers whenever a favourable situation has
been reached. The plant has now all it requires both in the way of
mechanical support and nourishment, and its lower part, thus rendered
useless, soon withers, breaking all connexion with the soil on which the
seed originally germinated. New branches continue to form, each one
producing additional suckers for the extraction of food from the host or
hosts, until a tangled mass of clinging stems is the result. Then the
globular clusters of little flowers appear, followed by balls of small
capsules which throw off their lids when ripe, allowing the seeds to be
shaken out by the wind. The Dodder plant now withers, leaving, in the
autumn, its dead tangles of climbing filaments still attached to the
withered herbs on which it fed, or to the branches of the tree which
served as its host.
Other parasitic plants possessing no chlorophyll, and therefore
incapable of building up organic compounds for themselves, derive their
food from the roots of trees and shrubs.
Among these is the Toothwort (_Lathræa_), which is carnivorous as well
as parasitic, and is described in our chapter (XXIV) dealing with
carnivorous plants, so that we need only refer here to its habit as a
parasite.
The seed of this plant germinates on the damp ground to which it falls
in early summer. The young root penetrates into the soil, deriving its
nourishment entirely from the food reserve that was stored up in the
seed, and soon sends out lateral branches in search of the roots of a
suitable host. If it fails to attain this end by the time that the
reserve is exhausted, it dies; but if it succeeds in reaching the root
of an Elm, Hazel, Hornbeam, Ash, Poplar, or other tree, it fastens
itself to it, and develops suckers which penetrate into the substance of
the root to extract its sap. The parasite now grows very rapidly,
producing its underground stems, with their fleshy, overlapping scales,
as described on p. 352.
The Broomrapes of the same order (_Orobanchaceæ_) are very similar in
their parasitic habits to the Toothwort, and, like the latter, they
possess no chlorophyll. The seeds germinate on the damp soil, producing
a long, narrow embryo that grows downward into the ground until it
reaches the root of some herb or shrub. It then gives off suckers which
penetrate into the root, and, with the aid of the organic food thus
obtained, forms a tuberous swelling on its surface. Flowering stems are
afterwards produced, and these, rising above the soil, bear terminal
spikes of lipped flowers, followed by capsules containing many seeds.
[Illustration: THE GREAT BROOMRAPE.]
Public-domain text, read in full here on John Shaqi.
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