of the forests growing now under similar conditions of position and climate. It was not in size that the plants differed though some that were forest giants then have but puny and dwarfed descendants now. There

were great and small then as now, but the average bulk and stature does not seem to have changed much through the ages. In that ancient forest where lizardlike reptiles crawled and dragon-flies darted about on a two-feet spread of wing—where no bee or wasp, no moth or butterfly, no bird or mammal, was ever seen, for they had not yet been evolved-in this forest there was not a single flower-bearing plant of the highest type. All that complex device for securing reproduction by means of seeds-that elaborate structure of infinite variety which we call a flower-had still to come into existence. The ruling family of that forest, trees a hundred feet high, were ancestors of the club-mosses that are now small herbs creeping along the ground. There were horsetails too, mostly great shrubs and trees, whose descendants, like those of the club-mosses, have shrunk greatly in size, ferns of many kinds, both great and small, fern-like plants bearing not spores but seeds on their fronds, cone-bearing trees of a type now extinct, and several other plants which have no descendants among living ones. This was the vegetation the fossil remains of which we find in the carboniferous rocks, and which, compressed to the hardness of stone and with its structure lost, composes our coal seams; and many millions of years ago as the carboniferous rocks were formed, we find even in that remote epoch a highly organized vegetable life.

In the beginning of the era which saw the evolution of flowering plants the most striking family is that of the cycads, fern-like, seed-bearing, but flowerless

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plants, represented at the present day by a very limited group. The great club-mosses and horsetails have been succeeded by smaller individuals of the same families, and none of the higher flowering plants have yet appeared. The rocks of this era are less rich in fossils, but trunks of cycads are sometimes dug up by the Portland quarrymen, who call them fossil crows' nests,' a name suggested by the short trunk hollowed at the top through the decay of the growing tip. One of these specimens, now in the geological department of the British Museum, is nearly four feet in height and three and a half feet in girth, but the trunk is usually much shorter.

In the latter part of the era the chalk rocks were being formed, and in them the fossils show that flowering plants have suddenly taken an important position. The lines of their evolution have not yet been clearly established, but a connexion is probable between them and the fern-cycad groups, and just before them the higher insects, bees, wasps, moths, and butterflies have appeared, a fact which probably has a direct bearing on their evolution. So much the most highly organized are they in the vegetable kingdom, and destined to take so dominant a place, that their arrival marks almost as critical a stage in the evolution of the plants as the appearance of man in the animal kingdom. The other plant groups shrink suddenly in importance. Cone-bearing trees are still present, but the species are far fewer than those of flowering plants, and the cycad representatives have become scarce.

In the era immediately preceding that of the present day that in which most of the existing mountain chains of Europe were built-a flora is found resembling the plants now living, and flowering plants have

assumed a predominating importance. At the present time they cover the face of the earth, adapting themselves to every climate, and finding a foothold in every position where plant life is possible. Of the other groups of plants only conifers hold their ground against them as forest trees in the higher latitudes of the Northern Hemisphere, and bracken and bog-moss cover considerable areas by reason of perfect adaptation to environment.

What is a flower-the evolution of which in a certain group of plants gave them the supremacy in the vegetable kingdom? It is a group of organs of reproduction, adapted for the securing of fertile seeds by means of animal and especially insect visitors, and it was in all probability the appearance of the higher insects on which its evolution depended. The lower classes of plants have neither flowers nor seeds; they are reproduced by spores. Such plants are ferns, club-mosses, horsetails, mosses, lichens, fungi, seaweeds, and most fresh-water plants. The higher plants are reproduced by seeds, but the cone-bearing trees (pines, firs, cedars, and larches) and cycads have no flowers, but naked seeds, while the higher flowering plants have a closed casket, formed of one or more specialized leaves, called the ovary, containing ovules, which are the future seeds. The ovules will be fertilized when the pollen formed on specialized leaves called stamens enters them. As the ovary is closed the pollen cannot get at the ovules directly as it does in conifers and cycads. It is received on a sticky surface called the stigma, sometimes erected on a long stalk called the style. The whole structure, ovary, style, and stigma, is called the pistil. Each grain of pollen dust must send out a tube long enough to reach down the style into the ovary until its tip can

enter an ovule, which is then fertilized and becomes a seed. It is by the perfection of their arrangements for securing the fertilization of the ovules and the success of their devices for securing the dispersal of fertile seeds that the flowering plants have triumphed over all the other families of the plant world.

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CHAPTER VII

PLANTS AND THEIR ENVIRONMENT

N spite of much that is still unverified in the history of the plants, we recognize four distinct eras in their development, though these no doubt merged

into one another by imperceptible stages:

1. The era of water plants, both fresh and salt. 2. The era of spore-bearing plants, such as ferns, club - mosses, horsetails, and primitive seed plants.

3. The era of cone-bearing trees, such as pines, firs, cedars, and larches.

4. The era of flowering plants.

As the higher families of plants evolved the lower groups were supplanted by them, and either ceased presently to exist, or, if they did survive, suffered a continual reduction in individual size and in numbers, and were driven to the more barren localities and those to which their structure happened to be specially adapted. Thus representatives of all the four eras exist at the present day, but the highly organized flowering plants outrank all the rest in number and importance because of their greater power of securing survival by adapting themselves to environment. Indeed, if instinct is defined as unreflecting action for a definite object, then it may be said that plants have instinct no less than animals, and since the protoplasm on which life depends is the same in both, animals without nerves