and many other flowers do not possess petals-they are fertilised by the wind. Every farmer knows the necessity for dry, fairly windy weather, when "the corn is on the bloom," for then the pollen is carried about. Every acre of wheat produces about 50 lbs. weight of pollen. If it happens to be wet weather,

a good deal of the pollen is washed to the ground, and never reaches the histils at all, so that they cannot be fertilised. Unless they are fertilised no seed-corn is produced. The weight or production of the grain crop depends on the number of the flowers in the ears which are effectively fertilised.

When a pollen-grain from one flower has been conveyed to the upper surface of the pistil of another flower, it is held there by a sticky matter which exudes. The

pollen-grain begins to sprout, just as if it were a seed, and buds forth a tube which has the power of making its way right to the base of the pistil.

That part is called the ovary, and if we examine an unfertilised pistil we shall see its base packed with little whitish-green, egg-like objects called ovules. These ovules would never come to anything,

FIG. 13. Magnified summit of the pistil of a flower, covered with pollen-grains.

and would be thoroughly useless, unless the pollentubes made their way right through the tissue of the pistil to where the ovules lie. Having reached and penetrated each ovule by a little opening called the micropyle, the contents of the pollen-grain are

poured out, and the ovules are now said to be fertilised. Each ovule begins to increase in sizein other words, to grow. The top of the pistil

usually withers, and the stamens always; and the vital energy of the plant, or what is left after expending so much in insuring cross-fertilisation, is thrown into the act of developing the ovules into seeds.

CHAPTER IV.

WOOD-CRAFT.

THE members of the vegetable kingdom exist amidst a mutual competition compared with which the worry of human life is a state of rest. This battle for existence goes on in addition to the attacks of numerous enemies of all kinds, which prey upon plants. Consequently, we cannot be surprised to find plants adopting devices to gain a livelihood as well as to escape enemies.

Such an adaptation on the part of plants to their environment has been going on through all those periods of geological time that have passed away since vegetable life first appeared on the earth. The modifications and specialisations of terrestrial vegetation have been increasing in complexity and completeness, and the vast variety met with in existing species of plants are the results of this long-continued and unbroken series of adaptations. Plants have now attained to a higher degree of mechanical specialisation than they ever before experienced.

I have chosen the heading of the present chapter to express certain special devices adopted by the higher plants to grow, escape enemies, and propagate their kind.

The giants of the forest have won in the battle of life by sheer strength and bulk. Their huge trunks lift the branches on high, and enable the leaves to hang out like green banners in the sunshine and the breeze. There is even a competition among the trees, individuals as well as species, which shall grow tallest. Who that has wandered through an unkept British forest has not been struck by the keen struggle going on among the trees for place and height? Not even in our overpopulated cities and towns are we so smitten with the fact that the weakest goes to the wall! One cannot explore a primitive wood without feeling that plants are as selfish and greedy as animals, not even excepting man!

The dense shade, which usually prevails in old woods and forests, allows but a scanty existence to those kinds of plants which have not been fortunate enough to accumulate sufficient woody tissue, to build up their stems into tree-trunks. The carbonic acid of the adjacent atmosphere is seized upon, firsthand, by the outstretched stratum of foliage overhead; and even if there were more of it, the umbrageous canopy prevents that admission of sunlight which, as we have already seen, is necessary to the stimu