THE BATTLE OF LIFE AMONG PLANTS. 
41 
phenomena in all cases, because a crop will fail on a particular 
soil after a while, and yet chemical analysis of that soil will 
reveal the fact that the particular elements required by a given 
plant are still contained in sufficient abundance in it. Land, 
for instance, that is “ clover sick ” — on which, that is, good crops 
of clover cannot be grown — is by no means necessarily deficient 
in the constituent required for the growth of the plant ; and, 
indeed, in the Eothamsted experiments the constituents in 
question have been supplied as manure, but without any good 
result. Again, root-excretions (assuming their existence) can- 
not be productive of injury, as we are assured by Dr. Grilbert 
that clover has been grown in the same plot of garden soil at 
Eothamsted for eighteen years in succession, while only a few 
hundred yards off no condition of manuring has hitherto been 
successful in restoring the clover-yielding capabilities of the 
land.* E everting, however, to the alleged antipathies of one 
plant to another, we may make passing mention of the curious 
circumstance recorded by M. Paul Levy,| that the lianas or 
climbing plants of the forests of Central America have their 
likes and dislikes, and that they will not attach themselves to 
particular trees even when brought into juxta-position with 
them. It is significant that the trees which are thus slighted 
by the twiners are just such as are ill-adapted for the support 
of such plants, being such as have tall unbranched trunks with 
smooth bark and a dense overhanging dome-like canopy of 
foliage. It is not only the climbing plants that refuse to grow 
on such trees, but to a less extent, also, the mosses, ferns, 
orchids, Bromeliads, and other epiphytal plants. 
It is obvious, from what has been previously said, that human 
interference affects these internecine conflicts of plants very 
materially. It is clear also that the cultivator can very often 
avail himself of them to his own profit. From this point of 
view the experiments and observations carried on at Eothamsted 
by Mr. Lawes and Dr. Grilbert are most important, especially 
those relating to the struggle among pasture plants, and the 
circumstances favouring certain plants more than their fellows. 
No detailed report of these particular experiments has hitherto 
been published, and only a few scattered notices in the Proceed- 
ings of the Horticultural Society (June 2, 1868) have appeared 
concerning them. We can, however, give some idea of 
their scope and nature by stating that a part of the park at 
Eothamsted, which has been under grass for centuries, has been 
divided into plots of equal size, placed side by side under con- 
ditions as nearly equal as possible. Some of these plots have 
* Journ. Hort. Soc.” New Series, vol. iii. p. 91. 
t Cited in Gardeners’ Chronicle,” 1870, p. 383. 
