THIS important point has just been put prominently forward in a thoughtful paper read by Mr William Ingram, gardener to the Duke of Rutland, Belvoir Castle, before the Leicester Museum, in which, with much felicity of illustration, he made manifest the action of certain laws affecting the decay of animal life, the consequent existence of impurities, and the necessity for their removal; and the further necessity for the corrective activity of vegetation as an important part assigned to plants in the great system of nature as sanitary agents. In the course of this address Mr Ingram pointed out the "great array of polluting forces" operating on the earth, and touched chiefly on animal life as a great polluting power. This it accomplishes in the continued residence of man and beast on the earth, in that matters corrupt and offensive are deposited, which, having "once formed part and parcel of the animal economy, cannot be applied again without infecting with their inherent corruption any living animal that may again absorb them; and also from the fact, that on the heels of decaying and dead animal life " treads decomposition; the dead matter that has once lived is distributed anew, and the fragments pollute the air, the water, or the earth." But in the operation of that wise economy that clothes all nature as with a garment of beneficent compensating services, vegetation interposes, and "Earth, that nourished thee, shall claim Thy growth, to be resolved to earth again; And, lost each human trace, surrendering up Thine individual being, shalt thou go To mix for ever with the elements.

To be a brother to the insensible rock And to the sluggish clod, which the rude swain Turns with his share, and treads upon. The oak Shall send his roots abroad, and pierce thy mould".

In life, the animal subdues the plant; when the former perishes, the plant reasserts its power; and so there is afforded the example of "two great dependent forces, mutually destructive, yet mutually regenerative; the one fixed to the soil would exhaust its resources of fertility, but the destruction of animal life restores its exhausted powers, and vegetable action goes on with renewed vigour".

Thus plants may be said to fulfil a true and great vocation; and this high service has two aspects, the one as regards dead nature, the other as regards living things. In its relations to dead nature, the plant serves, while living, to purify the air we breathe. It continually absorbs carbonic acid and gives off oxygen gas, and thus is a chief instrument in maintaining the natural condition of the atmosphere. It renders the air more fit for the support of animal life, both by removing that which is noxious, and by pouring into it that which is salutary to animal health and life. And when it dies, it either covers the earth with a vegetable mould, which favours the growth of new generations of plants, or it accumulates into beds of peat or mineral coal, by which man is long after to be warmed and the arts of life promoted. In either case, it only lingers for a while in these less sightly mineral forms. It gradually assumes again the gaseous state, and whether it is allowed naturally to decay, or is burned in the fire, ultimately arises again into the air in the form of carbonic acid. By this means, in part, vegetation is perpetuated upon the globe, and the natural composition of the atmosphere, as regards the proportion of the carbonic-acid gas, is permanently maintained.

As regards living animals, we all know and feel that plants are necessary to our daily life. Utterly dry up and banish vegetation from a region, and nearly every sensible form of animal life forthwith disappears.

There are also subsidiary purposes the plant serves, and one of these is that of covering and adorning dead nature. But this purpose is only secondary, and, as it were, ornamental, and yet has issues closely allied to sanitary purposes. One of these subsidiary purposes Mr Ingram has alluded to in a suggestive passage of his address relating to planting trees in our graveyards and cemeteries. Both the sanitary reformer and the teacher of aesthetics are asking that our graveyards be planted with trees; the one for the sake of the great purpose plants labour to fulfil as sanitary agents, the other as a means of ornamentation merely.

"Now they are scarcely known, And rarely in our borders may you meet The tall larch sighing in the burying-place, Or willow trailing low its boughs to hide The gleaming marble. Naked rows of graves And melancholy ranks of monuments Are seen instead".

On this point Mr Ingram remarks as follows: - "There is something more than sentiment in the custom, observed from remote ages, of planting trees in our graveyards and cemeteries. Trees are quickeners of decay - are the scavengers provided by nature for absorbing that which is corrupt in the ground, and quickening it into the life that gladdens our eyes in summer-time in green leaves and bright flowers: who would not rather that this ' mortal coil,' bereft of the life that gave it power, should reappear in verdure of the stately tree, the Cedar, the Pine, or the Oak 1 How much better than to contaminate the earth, or to poison the water-spring ? The ancient Egyptians sought to perpetuate the names and famous deeds of their great men by embalming their bodies, and placing them in almost impenetrable tombs. What have they gained but that destruction which nature has ordained, and which, though protracted, is nevertheless inevitable? Who knows or cares for the voiceless mummy 1 The men of ancient Rome destroyed their mighty dead by fire, and reverently placed their ashes in urns and tombs of sculptured marble, putting with the relics of their friends a small tear-bottle or lachrymatory.

If we continue to follow the custom of our forefathers, and return dust to dust, let us not omit to plant a tributary tree. Why should not our disused churchyards be planted 1 I am sure many persons would esteem it a privilege to be permitted to plant a tree on the grave of a dear friend. If this were done, our churchyards in time would be one shady grove, and would be so purified as no longer to be sources of disease to the living congregated around them".

What is here indicated is only a small part of the functions discharged by plants as sanitary agents. We have simply endeavoured to indicate Mr Ingram's line of argument, and to a small extent his conclusions. A large range of study is opened up to the intelligent observer, involving the whole area of vegetable physiology. In yielding food for the animal kingdom the plant is scarcely less a sanitary agent. One of the main objects of the plant is to feed the animal. This it does with various forms of vegetable matter in different climes and countries; and it provides for each herbivorous and carnivorous race those peculiar forms on which it best loves, because best fitted, to feed.