78 EXTIRPATION OF VEGETABLES. 
It is also asserted that no insect depends upon it for food or 
shelter, or aids in its fructification, and birds very rarely feed 
upon its berries: these are circumstances of no small import- 
ance, because the tree hence wants means of propagation or 
diffusion common to so many other plants. But it is alleged 
that the reproductive power of the yew is exhausted, and that 
it can no longer be readily propagated by the natural sowing 
of its seeds, or by artificial methods. If further investigation 
and careful experiment should establish this fact, it will go far 
to show that a climatic change, of a character unfavorable to 
the growth of the yew, has really taken place in Germany, 
though not yet proved by instrumental observation, and the 
most probable cause of such change would be found in the 
diminution of the area covered by the forests. 
The industry of man is said to have been so successful in 
the local extirpation of noxious or useless vegetables in China, 
that, with the exception of a few water plants in the rice 
grounds, it is sometimes impossible to find a single weed in an 
extensive district; and the late eminent agriculturist, Mr. 
Coke, is reported to have offered in vain a considerable reward 
for the detection of a weed in a large wheatfield on his estate 
in England. In these cases, however, there is no reason to sup- 
pose that diligent husbandry has done more than to eradicate 
the pests of agriculture within a comparatively limited area, 
and the cockle and the darnel will probably remain to plague 
the slovenly cultivator as long as the cereal grains continue to 
bless him.* 
* Although it isnot known that man has absolutely extirpated any vegetable, 
the mysterious diseases which have, for the last twenty years, so injuriously 
affected the potato, the vine, the orange, the olive, and silk husbandry, are 
ascribed by some to a climatic deterioration produced by excessive destruction 
of the woods. As will be seen in the next chapter, a retardation in the period 
of spring has been observed in numerous localities in Southern Europe, as well 
as in the United States, and this change has been thought to favor the multi- 
plication of the obscure parasites which cause the injury to the vegetables just 
mentioned, 
Babinet supposes the parasites which attack the grape and the potato to be 
