1222 
MESSRS. J. B. LAWES, J. H. GILBERT, AND M. T. MASTERS, 
with individual species growing separately, has there been absolute change in distinctive 
form by the use of various manures. Changes of degree are indeed sometimes very 
marked, as, for instance, in the tufts of Dactylis glomerata. Again, such changes as 
there are are chiefly in the organs of vegetation—roots, leaves, and stems, which show 
greater or less relative amount, precocity, permanence, and so on; whilst the changes 
in the parts of the flower are much less. It is probable that more attentive observa¬ 
tion would reveal differences in the processes of fertilization and in the germinating 
power as in the maturation of the seed. 
General Occurrence of Certain Species Hostile Competition or Peaceful Association. 
Certain plants occur with such frequency, and under such widely differing conditions, 
that it would seem as if they were in a great measure indifferent to the character 
of the soil or to that of the manure. There are indeed certain plants which if not 
crowded out by their more powerful neighbours seem to thrive on almost any soil and 
under almost any condition of manuring. The great extension of Festuca ovina under 
the most varied conditions of manuring is a case in point. We see illustrations of the 
constancy of occurrence, or of the same power of adaptation to varying conditions of 
soil, &c., in the case of wild plants generally. It is easy to pick out certain plants 
peculiar to limestone, or sandy or clay soils, as the case may be, but these are 
relatively few when compared with the large numbers that seem indifferent to the 
nature of the soil.* Again, observations of this character tend to show that it is 
the physical nature of the soil, its capacity for holding water and its permeability 
to roots, that are, in most cases, of greater importance than its more strictly chemical 
composition. It may also be stated, that plants growing in association with others of 
different species do not necessarily grow where the conditions of soil and climate seem 
to be, or are really most favourable to them individually, but in those localities where 
they can best maintain themselves in the competition with others. In a word, they 
do best where they can best adapt themselves to the combination of surrounding 
circumstances.t Any peculiarity of organisation which will help them in their struggle 
is of course a decided advantage. Such peculiarities, although they cannot be induced, 
may be, and are, enhanced by the action of manures. 
In the continual interuecine strife between plants, it is not always the resources of 
the plant itself which enables it to maintain or extend its ground. Its success 
* Masters, “ On the Flowering Plants of Oxfordshire,” Transactions of the Ashmolean Society, 1857. 
For a summary of our knowledge on this matter, see Alph. de Candolle, ‘ Geographie Botanique,’ vol. i., 
p. 423 ; and the more recent researches of Contejean, Ann. Sc. Nat. Bot., ser. 5, t. xx., p. 266, and ser. 6, 
t. ii., p. 223. While there is great difference of opinion as to the relative influence of various soils on 
plants, all are agreed that, with certain obvious limitations, the majority of plants are “indifferent” to the 
chemical or physical nature of the soil. 
f For some general remarks on the conditions of the struggle, see the chapter on the extinction of 
species in the late Sir Charles Lyell’s ‘ Principles of Geology,’ and that on the struggle for existence in 
Darwin’s ‘ Origin of Species.’ 
