THE BATTLE OF LIFE AMONG PLANTS, 77 



leguminous plants at another ; so that, in the course of thirty years, 

 the author whose observations we are citing was witness of five or six 

 such alternations. 



It follows from all this that a plant, as was pointed out by the 

 late Dean Herbert, does not necessarily grow in the situation best 

 adapted for it, but where it can best hold its own against its hos- 

 tile neighbors, and best sustain itself against unfavorable conditions 

 generally. 



The sources of success in the contest are manifold ; they vary more 

 or less in each individual case. Probably they are never exactly the 

 same; nevertheless, there are certain circumstances which must always 

 be operative in conducing to the victory. A few illustrations must suf- 

 fice. It is easy to understand why first-comers, duly installed, should 

 have an advantage over later visitants ; why the more prolific should 

 outnumber the less fertile ; and how it is that a perennial plant has a 

 better chance on any given spot, center is paribus, than an annual, whose 

 progeny would find the ground occupied, and their chances of sur- 

 vival materially interfered with by their longer-lived neighbors. 



Again, there is no difficulty in understanding why such plants as 

 quitch (Tritlcum repens) or bearbine {Convolvulus sepium) hold their 

 own so tenaciously, and so much to the prejudice of their neighbors. 

 The long, creeping, underground stems, rooting, or capable of rooting, 

 at every joint, give them an immense advantage over plants not so 

 favorably organized. The ends of the shoots of the convolvulus, more- 

 over, dilate into tubers, which are thrust into the ground, to form in 

 the succeeding spring fresh centres of vegetation. A great rooting- 

 power is obviously of great benefit ; not less so is an extensive leaf- 

 surface. It is not only that the copious feeding-roots absorb the avail- 

 able nourishment from the soil, not only that the wide leaf-surface 

 avails itself of every ray of sunlight, every whiff of air that plays over 

 it, and thus serves to build up the tissues of the plant to which the 

 root or leaf respectively belongs, but they practically oust other plants 

 less favorably circumstanced than themselves. The roots occupy the 

 soil, and rob the weaker plants of their share of its resources. The 

 tree with dense foliage shuts off from its lowlier neighbor much of the 

 light and air necessary for its existence; and hence, in a measure, the 

 absence of vegetation in pine-forests or under the shadow of dense 

 woods. Some plants there are specially organized to resist and over- 

 come these hostile conditions. Among them are the climbers, the 

 twining plants, and those with tendrils of one sort or another. The 

 bramble or wild-rose, with its slender, arching, hook-beset branches ; 

 the wild-hop, with its coils of cord-like sprays ; the clematis, clinging 

 on firmly by means of its leaf-stalks to any thing it can lay hold of; 

 the ivy, grappling with the trunk of a tree all these are, in some 

 sense, weakly plants ; they would be overweighted in the struggle with 

 their stronger neighbors, if it were not for the special adaptation of 



