where they are absorbed, through the stem to the leaves. And at whatever parts of the plant the nitrogenous and mineral constituents derived from the roots are combined with the carbon fixed in the leaves, the resulting compound must be diffused thence in order to reach the deep-seated cells, such, for instance, as those of the cambium [multiplying] layer, and those of the roots which are growing and multiplying and yet have no power of extracting carbon directly from carbonic anhydride. In fact, those cells which contain no chlorophyll and are out of the reach of light, must live after the fashion of torula, and manufacture their "protein" out of some material other than carbonic acid. "Thus the higher plant combines within itself the two physiologically distinct lower types of the fungus and the alga."

It is considered probable that all vegetable cells at some stage of their development manifest a curious circulation of their protoplasmic contents known as cyclosis. This consists in the steady flow of one or more currents of protoplasm over the inner surface of the cell wall. One of the most striking instances of this occurs in the cells of Valisneria spiralis [Figs. 43 and 44]. Another in Anacharis alsinastum, a

very common and obnoxious water weed. The most interesting cases are perhaps the following: nitella is a small water weed composed of exceptionally large cells whose envelope is transparent. It is therefore possible, under a very moderate power, to observe the flow of the protoplasm. The terminal cell of the leaf is of a cylindrical form, tapering suddenly to a point at the extremity. Under a moderate power, this cell looks about one inch and a half broad before it begins to taper. The whole surface of the cell, which is colorless, or almost so, is studded in a perfectly regular way with tiny bright green spots, except along two lines, which run from the base to the apex and on opposite sides of the cell. Suppose one of these green-studded sides to be turned toward the eye; a steady current of colorless protoplasm may be seen flowing down one side of the leaf, bending back at the point, and flowing up again on the other side. In this current are borne a large number of irregularly shaped masses of brilliantly but delicately colored green protoplasm. Among these are scattered other curious protoplasmic masses: round green balls, beset with spines of the same color, like a spherical sea-urchin, or a lively chestnut burr, carved in miniature, of pure emerald. There are, of

course, two lines along the longitudinal direction of the cell where the edges of these two opposing currents touch, and where their motion is neutralized; these two neutral lines are those before spoken of as not marked by the fixed green studdings. Now turn the cylindrical leaf half over on its side, so that one of these neutral lines is toward the eye. The protoplasmic current can then be seen pouring down one side of the inner surface of the leaf, and up the other, bearing its lovely green craft upon and within its bosom.

Almost as beautiful an example of cyclosis may be seen with a low power of the microscope in the purple hairs of the tradescantia, or in those of the common nettle. The current itself is colored in that case, and bears no bodies along with it, but the beauty of the delicate amethystine flood can scarcely be surpassed.

Many other curious phenomena in plant life, such as the chemical effects of heat, light, and electricity upon growth, the wonderful means by which plants climb and cling, the movements of roots and stems and leaves as they grow, must all be omitted for want of space.

T

CHAPTER VII.

CORN AND ITS CONGENERS.

HE ferns conclude the series of vascular crypto

gams, and introduce us to the highest group in the vegetable kingdom, the phanerogams. The nearest term which popular language supplies to designate these plants is the flowering plants, though this is not strictly accurate. All the common forest and fruit trees, the flowering shrubs and plants, are included in the group, but many other less familiar forms also find place here.

The dim prophecies that have been struggling for utterance through all the language of vegetable life, here find their fulfilment. The root, which had no representative in the single-celled plant or the filamentous, algae, which was represented by the mycelium of the fungus, the root-hair of the liverwort and the mosses, has reached the more complex rhizome in the ferns, but still falls short of the specialization which determines the true root of phanerogams. A similar process of development in the stems of

plants may be watched from its earliest beginning to the wonderful bundles of spiral, pitted, scalariform, and sieve vessels of the ferns which make its fibro-vascular system, and ally it to the still greater perfection found in the flowering plants and trees. If this slow blossoming out into the ideal type, in the vegetable kingdom; this reaching through infinite varieties and species and genera toward the highest expression of plant-life, could be studied through all its intermediate forms, the continuity would seem more remarkable than is possible when only certain groups are selected for examination. These groups are the most prominent, it is true, and are arranged in correct order, but they are not a sequence, and it is impossible by the closest study of links here and there, to take in fully the idea of continuity-to see clearly the wonderful chain that binds into unity the dimmest ages of the geologic past with the present day;--the humblest vegetable cell that finds its world in a drop of water, to the noblest tree that grows in the primeval forest.

While there has been this steady development in type, there has been along with it many minor fluctuations; forms that now occupy a low position in the scale, once reached enormous magnitude