Vegetable physiologists are now turning their attention to the great cause of the evils that plants are heirs to, and which has been so long neglected. The microscope is revealing the actual condition of the root, and explaining its mode of growth. Dr. Lindley, in a late Gardener's Chronicle, says:

"It has long been known that in certain plants the end of the roots is covered by a kind of cap or hood, within which the process of growth is carried on. Of this the common Duckweed offers a familiar example, which any one may see with the aid of a pocket lens. Another, on a far larger scale, is to he found at the end of the stout aerial roots of the Screw Pine (Padanut), in which it looks like a great brown cup. It now appears that the structure in question is general, not exceptional Mr. Henfrey finds that 'the growing point of a root is nut at its absolute extremity, which is covered by a cap-shaped or hood-like portion of epidermis of its own. continuous likewise behind with the cambial structure. This cap-like sheath of the point of the root may be compared with the head of an arrow, forming a firm body, which can be pushed forward by the growing force behind, to penetrate through the resisting soil. This cap is subject to destruction and decomposition by external agencies, and is less distinctly seen in roots growing in earth than those of aquatic plants.

In all cases it is constantly undergoing renewal by cell-development at the back-part; and when it remains undissolved, as in many water-plants, it becomes very large; when it undergoes decomposition in proportion as it is renewed behind, it presents an irregular, ragged appearance, which probably gave rise to the idea of a spongy structure at the ends of the rootlets.'"

The ends of roots undergo a process of exfoliation, the rapidity of which depends on the idiosyncracy of the species, and the temperature and moisture to which they are exposed. This exfoliation is connected with the formation of new tissue in the viscous matter, beneath skins or hoods of epidermis, which are eventually thrown off, and the doctor proceeds thus to point out the practical value of this apparently small fact:

" That rootlets form a skin at their points beneath which the process of growth is carried on may be an anatomical fact, but what is its application 7 Of what consequence can it be to a gardener to know what a microscope and a microscope only can reveal? We answer by asking whether the invisible processes or digestion in the human stomach, need not be understood because they cannot be seen 7 or whether it is perfectly indifferent to a gardener to know where the equivalent of a stomach is to be found in the plants he grows because it is impossible for him to view either the processes of assimulation themselves or the minute places in which they go on? Surely it must be admitted that if we are to understand the mode of treating plants properly we cannot learn too much about their ways of life and growth.

"It is well known that the roots of plants increase in length solely by the continual addition of new matter to their points. Were it otherwise they would be bent and turned and distorted by the resistance of the soil itself, if indeed they could ever penetrate it at all. This will be easily seen by any one who endeavors to force a piece of twine through the loosest and softest earth that can be found. Hence the well understood fact that the youngest part of a rootlet is its tip, a part which is incessantly renewed during the period of growth; and which, acting like a sponge in absorbing whatever the earth can give up, had acquired at one time the name of spongiole, spongelet, or little sponge. But there always remained these questions: how does the soft young delicate nascent tissue of the rootlet manage to exist in contact with the earthy particles that it is perpetually displacing? and why does it never catch up such particles and entangle them in its substance? To this an answer is now returned; it is not, it is never, in absolute contact with the earth, but is screened from the earliest moment of its second life by an old skin, which it pushes forward, and gradually renews, forming its own matter of growth in security beneath it.

Mr. Henfrey compares the skin to the head of an arrow, which can be pushed forward by the growing force behind. We would rather compare it to a screen or mantlet such as troops sometimes employ in their advance towards an enemy.

"We may safely assume that this cap, hood, coif, screen, or whatever else it is called, is necessary to the root, and that its removal must be injurious, inasmuch as the forward growth of the root will be prevented by its removal. That being so, of what immense importance it must be to secure, with the utmost care, this delicate organization on the safety of which so much depends. In the rude hands of ignorant persons, who transplant a bush by pulling it up, as if ey were 'pulling a turnip,' all this important structure must necessarily be destroyed. It is no wonder then if so many plants perish under the hands of common laborers. Only see how they 'prick out' cabbage plants or celery, or any of the seedling tap-rooted crops; it is no wonder if they find great gaps in their rows. Instead of wreaking their anger on ' the grub they should blame their own ungentle ways.

"Hut it may be said that plants are dealt with well enough in the rude mode that is so common, and that the care required by theory is not really demanded by practice. Winter-moved shrubs, or those which bear to be lifted in August without much care, may be pointed to in support of this notion. But these instances do not really affect the question. In the dry weather of August such plants as the Rhododendron and its allies are not growing; their roots are ripened, hard, and tough to the points of the fibres; and they will bear much rough usage without damage; moreover, a large part of their most delicate fibres is so firmly imbedded in earth that they come up with a ' ball,' and are not at all disturbed. So in winter, when trees are removed, the rootlets are hard and torpid. Nor is it to be forgotten that some plants have a wonderful power of repairing injury, if they have once acquired their woody organization, and time is given them. When the roots of a winter-moved tree are broken the wounded ends may close up. and on the sides of the roots new rootlets with the requisite hood will gradually form before the period of vernal growth recurs.

Others are constitutionally able to reproduce roots at all seasons, and under all circumstances, owing to what is called their strong vitality: as we see in the Willow, whose wands grow when stuck in the earth, although they neither have nor ever had a root.

"It is not to cases such as these that rational gardeners will look. We once knew a man who ate Belladonna berries with impunity; that was his constitutional peculiarity; his stomach was able to resist that dangerous poison; but we cannot infer from such a case that Belladonna berries may be eaten. So with the roots of plants; we are not justified'in saying that the utmost care is not required to preserve their young points from injury because some plants succeed perfectly well without care.

"But it is not merely on account of the extreme delicacy and importance of their points that roots require to be handled with the utmost gentleness. Another microscopical fact has been ascertained within the last few years, and is of hardly less interest. When you look with the naked eye at the skin of a young root-fibre, nothing is seen except an apparently level, uninterrupted surface. But in many cases there are present infinite multitudes of little hairs, through which food is imbibed; they are the mouths of the root. Through their agency the sucking or feeding power of the rootskin is very considerably augmented; to remove them is to diminish or destroy that power. But they are so delicate that any nngentle treatment of the root must destroy them. In the words of Prof. Henfrey,' they are mostly invisible to the naked eye, and their presence is chiefly betrayed by the adhesion of the soil to them. When young roots are carefully washed and placed under a magnifying glass, their fibrils (root-hairs) are seen very clearly; and on such roots as those of barley, for instance, they exist in enormous numbers.'

"We recommend all unsuccessful cultivators to turn these important facts over in their minds, and to consider well whether they have always thought about them. They have a very large application".