CLIMBING PARASITES. GREEN-LEAVED PARASITES. TOOTHWORT. 179 
grass at such places would be injured. This conclusion appears to be supported 
by the assertion of the country folk that after the season when the Eyebright is in 
full bloom, the cows yield less milk, a fact which explains the German name of 
“Milchdieb” (milk-thief) popularly given to the plant. The diminution in the 
quantity of milk yielded is, however, certainly connected with other circumstances. 
It depends especially upon the universal abatement of the growth of grasses in 
early autumn and the consequent curtailment of the food afforded by the pastures. 
The injury done by the Eyebright to its hosts by the withdrawal of nutriment 
and destruction of rootlets cannot be very considerable, for the appearance of the 
grasses and other host-plants, which are affected, is not noticeably different from 
that of the plants of the same kind which escape invasion. 
The same statement is true in the case of the various species of Lousewort 
(Pedicularis), almost all of which are meadow-plants; that is to say, they are 
present in great abundance in upland and alpine pastures without apparently 
injuring the species growing in their company and used by them as hosts. Unlike 
the species of Cow-wheat, Yellow-rattle, and Eyebright, however, nearly all the 
Louseworts are perennial, and accordingly differ from them also in the construction 
of their suckers. There is, it is true, no difference in shape between the suckers of 
the Cow-wheat and those of Pedicularis, but they are dissimilar in respect of size 
and place of origin. The suckers of the perennial Louseworts are barely more 
than half the size, and are only developed near the attenuated extremity of a 
rootlet. They are very few in number; each of the long, thick, fleshy rootlets, 
proceeding from the base of the stem usually produces a single sucker only which 
settles upon the root of a suitable host-plant in the same way as the suckers of 
Cow-wheat. By the time that the parasite’s fruit ripens, the piece of root which 
has been invaded has usually already turned brown and fallen into decay. Now in 
the case of Cow-wheat it may undoubtedly be immaterial whether the piece of root 
attacked by it is living or not when its fruit is ripening, inasmuch as its own 
annual root rots as soon as the seeds have been produced from the flowers above 
ground. But with Pedicularis it is different. The perennial roots of this plant 
require a host to nourish them next year, and when the piece of a host’s root which 
has been attacked and sucked as a nutrient substratum one year dies, the sucker 
belonging to the root parasitic upon it is no longer in a position to fulfil its function 
by continuing to absorb fresh juices. Suckers thus reduced to a state of quiescence 
soon perish, and only leave little scars to indicate the places where they existed. 
The perennial root of the Pedicularis has now to seek a new source of nutriment, 
and this is effected by the elongation of its tip, which continues to grow until it 
reaches the living root of another plant suitable as host, whereupon it develops a 
fresh sucker upon that root. This elongation doubtless requires a large quantity of 
plastic materials; but these are found stored in abundance in the older parts of the 
parasitic root. 
These circumstances explain, at anyrate in part, the characteristic structure and 
disproportionate length of the roots of Pedicularis. From all round the short erect 
