potash in the soil, and of 2,503 lbs. and 4,778 lbs. per acre of total phosphoric acid, appears from these results to be immaterial as a measure of present soil fertility, notwithstanding that the degree of solubility of each constituent is largely increased on the different plots according to the manure employed. As no nitrogen has ever been applied to the plots of the mineral series (1 to 40) there has been no strain on the natural resources of the soil, and consequently the barley crops obtained have been small.

From the next group of plots, 1 A to 4 A, we get some valuable information. To each of these portions of ground ammonium salts have been added to the other manures. (See Table VII. [a].) · The total amount of potash is seen to range from 35,845 lbs. to 43,301 lbs. per acre; of this quantity the soluble part ranges from 50 lbs. to 1,029 lbs., showing that plot 3 A has 200 times more available potash than plot 1 A, but, owing to the lack of sufficient soluble phosphoric acid, the yield of barley is but 2 bushels per acre in excess of plot 1 A. The phosphoric acid ranges in total amount from 2,452 lbs. to 4,602 lbs. per acre, the soluble portion from 152 lbs. to 1,264 lbs. per acre. The produce of barley grain and of barley straw is seen to be about doubled from the previous series; but in plot 1 A, receiving ammonium salts alone, there is a starvation of the two mineral constituents, potash and phosphoric acid, notwithstanding the large amounts in the soil; while in plot 3 A, receiving the nitrogen and potash, but no phosphates, there is a starvation of phosphoric acid, with a consequent falling-off in the crop grown.

Plot 7, which had received 14 tons of farmyard manure per acre for thirty-eight years, amounting to the enormous quantity of 532 tons of manurial material, but made up very largely of organic matter and water, shows an accumulation in the soil of 33,374 lbs. of potash per acre, of which 669 lbs. only is soluble. Phosphoric acid shows 3,669 lbs. per acre, of which 932 lbs. are soluble. The returns of corn and straw on plot 7 show that the accumulated residue of organic nitrogen in the soil enables the crop to be maintained at a high standard, notwithstanding that the amounts of potash and phosphoric acid in the top 9 inches of soil are lower than in the soils receiving artificial But doubtless the improved subsoil on the dunged plot would have much to do with its increased produce.

manures.

HOW PLANTS ARE DEPENDENT UPON THE FOOD SUPPLY IN THE SOIL.

The invaluable investigations of Rothamsted just referred to, and others of a similar kind, illustrate this fact among others -that the crop or particular plant we grow has to do not only with the supply of food in the soil as a whole, but also with each of its ingredients separately. The total productive power of a soil cannot exceed its power to supply to the growing plant each and all the necessary food constituents. Every plant we cultivate must have a certain amount of each of the nutritive elements-potash, phosphoric acid, and nitrogen-or it cannot grow satisfactorily. Thus the plant cannot rise above the level of the lowest ingredient in the food supply. If each description of food comes up to the required standard, and other conditions of heat and moisture are favourable, a good result may be expected; but if any one element falls below this standard, the growth of the crop must suffer.

We have seen in the various illustrations brought forward that the food supply available to plants varies greatly in different soils. Sometimes one constituent and sometimes several may be lacking. An horticultural soil may have a proper texture, with a suitable amount of moisture, and, in fact, a full supply of everything the plant needs, except phosphoric acid; if so, it cannot yield a full crop. Add phosphate in an available form and the growing plants will be benefited. Another soil may be deficient in potash, another in lime, another in nitrogen, still another in two or three of these substances. This same variation, as shown in Table VII. (b), may run through inherent fertility of the soil and in the solubility of its constituents. Therefore an horticultural soil may be deficient in available mineral ingredients or in available nitrogen. Or it may be so compact that air and moisture cannot get into it to work over the crude material it contains, nor the plant roots make their way through to obtain the food that has been made soluble. Again, it may be so loose and non-retentive that the food constituents will escape by drainage. Or, on the other hand, it may be so dry that fertilisers will be useless, and plants wither for lack of moisture; or so wet and cold as to prevent plant growth. In these several cases proper tillage operations will assist in amending the

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soil texture. Its power of holding water may be improved; its supply of available plant food increased; and then by a suitable manurial treatment it may be brought into condition to yield bountiful returns for all that is done to it.

The next question very naturally is, What ingredients of plant-food are most frequently deficient in horticultural soils?

I think we may take it as a pretty-well established fact that the only constituents of plant food which need be supplied to garden soils are potash, phosphoric acid, lime, and nitrogen, When we say these ingredients are lacking, we do not mean that the soil does not contain them, but that it does not supply the growing plants with as much as they need. It is not so much because horticultural soils have been worn out of plant food, but rather because the food is locked up in such combinations that the roots cannot get at and use it, that an artificial supply of soluble food in manure becomes necessary.

CONCLUSION.

In conclusion, a few practical remarks may be made upon the three main constituents of plant food in horticultural soilsnamely, nitrogen, potash, and phosphoric acid.

Nitrogen. Although the nitrification in rich garden soils, leaf-moulds, and peat-moulds may be sufficiently active for the gardener to dispense with artificial nitrogenous manures in most cases, yet there are certain species of plants which rapidly develop a large mass of foliage, and these cause a rapid and extensive demand upon the available nitrogen of the soil. For such plants it will always be advisable to use nitrate of soda, sulphate of ammonia, guano, soot, or similar materials as manure; and also for growing very early crops, or plants out of season.

Phosphoric Acid.-Assimilable phosphoric acid occurs in very small actual quantities in most soils, however rich; this has been fully illustrated in the tables. It is therefore necessary to add this ingredient by a manurial application if full crops are to be obtained. The best form in which phosphoric acid may be added to horticultural soils is by bone phosphate, bone meal, double superphosphate, or basic slag. Superphosphate of lime yields a certain proportion of phosphoric acid soluble in water. But in rich moulds cheap mineral superphosphates are not to be

recommended, being always more or less acid; and this introduction of sulphuric acid into soils poor in lime would certainly be hurtful to growing plants.

Potash.-Rich horticultural soils contain a considerable proportion of potash, which becomes only slowly available for vegetation. For certain cultures-more especially that of ferns, palms, vines, roses, potatos, &c.-potash manures have a very beneficial effect when applied to leaf-mould composts. The most rational mode of application is to use carbonate of potash, one of the chief ingredients in wood ashes; kainit salt, sulphate of potash, or muriate of potash may also be used. Potash is retained by the soil, and plants are able to absorb it as they need. The proportion to be used must vary according to the requirements of the plants cultivated.

ON THE FLORA OF AUSTRALIA.

By G. H. ADCOCK, F.L.S., F.R.H.S.

I HAVE often tried to imagine what must have been the feelings of Mr. (after Sir Joseph) Banks and his companion, Dr. Solander, as they the first scientific investigators of living Australian plants-gazed on the enchanting beauty and rich floral profusion which aptly suggested the name "Botany Bay." Fancy an enthusiastic botanist in the present day finding himself in a new land with a flora so unlike that of any other.

In attempting even a sketch of our splendid flora at the request of the ever-courteous Secretary of the Royal Horticultural Society, it is with the consciousness that the subject requires an abler pen than mine to do it anything like the justice to which it is entitled.

In the "Second Systematic Census of Australian Plants," published in 1889, my esteemed friend the late Baron von Mueller included among the Vasculares 8,839 indigenous species. Of these he gives 7,501 as endemic to continental Australia and Tasmania; so that in round numbers 85 per cent. of our plants are exclusively Australian. The area is, roughly speaking, about 8,000,000 square miles, much of it presenting almost insuperable

difficulties to the work of collecting. All zones of plant life are here represented, from the Alpine vegetation to the luxuriant and varied flora of the tropics; and it is a record of which we who have made Australia our adopted home may be reasonably proud that so many species, totally different in so many respects from those included in other and better-known floras, have been so closely observed and so carefully and accurately described. When we consider that there are countries-each with a history going back far beyond the commencement of the Christian era, each the birthplace of generations of eminent scientific menthat have never yet had their floras described as systematically as ours, we cannot but feel the deepest admiration for the scientific genius, perseverance, and research by means of which such splendid results have been achieved. Australian botanical science presents an illustrious roll of indefatigable workers.

It is a matter of great regret that so many of the names bestowed on native plants and animals by the pioneer settlers are singularly inappropriate. Thus "Gum-tree" is the colonial name for all species of Eucalypts. The Banksias are known as Honeysuckles." Our native "Fuchsia" is a Correa belonging to the Rutacea. Exocarpus cupressiformis is the native "Cherry." "She Oak" is the name given to some of the Casuarinas, whose cone-like fruits are called "Oak-apples." Australian Tea-trees" are members of the order Myrtacea, and include plants belonging to the genera Melaleuca and Leptospermum, while "Native Hops" represent various species of Dodonca and Goodenia, or maybe Daviesia latifolia. And so this list might be almost indefinitely extended.

The flora of Australia presents many peculiarities, of which much capital has often been made. Thus our trees are, many of them, peculiar in giving but little shade. Some are leafless. Our Cherry is stated to grow its stone outside the fruit-really on a succulent fruit stalk—while our Pear (Xylomelum pyriforme), one of the Proteads, is not only wooden but reversed on its stalk, and our Nettle assumes the proportions of a fair-sized tree up to 100 feet in height, and so we might go on.

The first thing that will probably strike a botanical observer in Australia is the great extent and wide distribution of its forests, composed chiefly of Eucalypts, which form the principal timber vegetation of the continent with perhaps the exception