172 CLIMBING PARASITES. GREEN-LEAVED PARASITES. TOOTHWORT. 
A comparatively large number of species, i.e. twenty-five, are distributed through 
central and southern Europe. A few have been introduced recently for the first 
time with seeds from the New World, as, for instance, C. corymbosa, which was 
accidentally conveyed with lucerne seeds from South America to Belgium, and has 
latterly begun to range over central Europe. 
The various species of Cuscuta attack chiefly small herbaceous, suffruticose, and 
shrubby plants; but a few American species coil themselves round branches growing 
at the top of the highest trees. Notice has been especially drawn to certain 
European species on account of their disastrous effects upon cultivated plants. The 
most famous is Cuscuta Trifolii, known as the Clover-Dodder, the appearance of 
which in clover-fields causes so much anxiety to farmers, and which is so difficult 
to exterminate. Another unwelcome visitor is Cuscuta Epilinwm, which coils 
round flax stems and hinders their growth, and a third species, Cuscuta Ewropea, 
sometimes ravages hop-plantations. This last is, indeed, the most widely dis- 
tributed of all the Cuscutas, and extends from England over central Europe and 
Asia to Japan, and southwards as far as Algiers. It is parasitic not only on hops, 
but also on elder, ash, and various other shrubs and herbs; in particular it exhibits 
a preference for nettles. 
The seeds of this species, and of Dodders in general, germinate on damp earth, 
on wet foliage undergoing putrefaction, or on the weathered bark of old trunks. 
The seedling, which in the seed lies imbedded in a cellular mass full of reserve- 
food, is filiform and spirally coiled. It is twisted once, or once and a half, and 
is thickened at one end like a club. In true Cuscutas, no trace of cotyledons 
is to be perceived, nor does one find vessels in the interior of the seedling; but 
chains of cells arranged with great regularity are noticed in the axis of the filiform 
body, and are easily distinguished from the surrounding cells. In nature, the 
seeds, after falling to the ground and lying there through the winter, do not 
germinate till very late in the following year, i.e. at least a month later than the 
majority of the other seeds reaching the same ground simultaneously with them. 
Perennial herbs, also, have, by the time that germination takes place, already 
developed shoots from their subterranean roots or rhizomes above the surface of 
the ground, later a circumstance of great importance to the parasites. If a 
Cuscuta were to germinate early in the spring, it would not readily find close by a 
support up which to twine; whereas later, there is seldom any lack of annual stems 
or shoots of perennial plants in the immediate neighbourhood. 
When the twisted embryo germinates, it stretches and at the same time revolves 
from right to left, assuming the shape of a screw and pushing its lower clavate 
extremity out beyond the coat of the seed (see fig. 34"%%*%°). This extremity forth- 
with grows into the earth and fastens tightly on to particles of the soil, withered 
foliage, and other objects of the sort. The other, attenuated extremity of the 
filiform seedling, which is still wrapped in the seed-coat and the mass of reserve- 
food, lifts itself up in the opposite direction, avoiding such solid bodies as it may 
happen to encounter, and grows in a curve round them. Further growth does 
