MANURma IN THEOEY AND PRACTICE. 



Ill 



striking, as ithas noble foliage of a rich glaucous blue- 

 green. Aralia Sieboldii (correct name Fatsiajaponica), 

 too, must not be forgotten, as it is quite hardy in 

 sheltered places, and has splendid foliage which is very 

 distinct in appearance. A. papyrifera (correct name 

 Fatsia papyrifera) is even more noble, but, as it is 

 not hardy, plants should be taken up in the autumn 

 and wintered in a cold house or shed. The New 

 Zealand Flax [Phormium tenax) is also a fine plant for 

 the hardy fernery, and there are many others that 

 may be used with good effect ; while as to ferns 

 beyond those mentioned, their name is legion, and, 

 as they cost but little to collect or puix'hase, any one 

 may soon start with a good stock of some of the 

 principal sorts. The best time to do this is early in 

 the spring, just before the young fronds start, when 

 they not only bear up-rooting without suffering- 

 much injuiy, but they may be split apart and 

 divided, and so increased, the only limit to this 

 being the number of separate crowns, each one of 

 which, if carefully removed, will soon form fresh 

 roots and grow. Some kinds being more tender 

 than others, it is necessary to afford protection 

 against spring frosts, and keen cutting winds, 

 especially if the fernery is not naturally well shel- 

 tered, as when the fronds are just fonning and 

 unfolding they are easily injured, and if damaged 

 then, are disfigured for the rest of the season. The 

 easiest way of protecting ferns, and perhaps the 

 most effectual, is to stick in a few Laurel or other 

 evergreen branches around the north-east sides of 

 each plant, and leave them there till all danger is 

 over, w^hen they should be cleared away and the 

 surface of the ground cleaned by being freed from 

 weeds, and then mulched by placing a good layer of 

 leaf-soil over the roots of the ferns. This will act 

 very beneficially, as, besides affording much extra 

 food for the plants, it will also assist most materially 

 in keeping the earth moist, as, being of a non- 

 conducting nature, it prevents evaporation, and 

 therefore when water is given it tells. 



AMiat ferns much like is damping over-head, 

 which is the best way to apply the water, and if it 

 can be done frequently during the summer, at any 

 time in the evening, the plants wdll keep in luxuriant 

 health. 'WTiat injures them and makes them shabby 

 sooner than anything else is the red spider, a tiny 

 insidious insect that makes its appearance in diy 

 weather ; but if water is resorted to, and adminis- 

 tered in the manner mentioned, the damping will 

 prevent the red spider doing much harm, as it keeps 

 the insect on the move, breaks up its web, and thus 

 stops its increase. 



Many gi-owers of ferns clear off the fronds in the 

 winter : but that should not be done, as, by dis- 

 robing the plants then, they are left naked at a time 



•when they most need their natural covering. 

 Instead of remo^dng the old dress, it is far better 

 and wiser to add to it by placing over the crowns a 

 few fresh-fallen leaves, cocoa-nut fibre, or common 

 Bracken, which should remain till the young growth 

 pushes its way through in the spring, when th& 

 general clear-up may begin. 



MANUEING IN THEORY AND 

 PRACTICE. 



Bt JoHjr J. Willis. 



How Soils become Fertile. — Many inves- 

 tigations have been made during recent years 

 as to the mode in which nitrification takes place,, 

 because ammonia, as such, cannot exist for any 

 length of time in the soil. It rapidly becomes 

 converted into nitric acid, in which form it is most 

 invaluable to the gardener as a plant-food ; and the 

 loss of nitrates by drainage is one of the most 

 serious difficulties with which the tiller of the soil 

 has to contend. 



What, then, are the sources of the nitrogen of 

 vegetation ? Are they the same for all descriptions 

 of plants ? Are they to be sought entirely in the 

 soil or entirely in the atmosphere, or partly in the 

 one and partly in the other ? 



These are some of the questions which Lawes and 

 Gilbert have endeavoured to solve by a series of 

 investigations extending over a period of forty 

 years, and in which they are still engaged ; for, 

 although their researches have thrown much light 

 on these questions, they involve great difficulties^ 

 and a vast field of scientific inquiry is still left 

 open ; and, no doubt, much laborious work has yet 

 to be accomplished before these questions can be 

 satisfactorily answered in all their bearings. 



From the experiments already made it appears 

 that the bodies yielding nitric acid in the soil are 

 — first, the various nitrogenous organic substances 

 which arise from the decay of vegetable or animal 

 matter; and, secondly, ammonium salts, either pro- 

 duced in small quantity duiing the decay of organic 

 matter and carried to the soil by rain, or, in some 

 cases, applied intentionally as manure. A fui-ther 

 soiu'ce of the nitrates contained in the soil is to be 

 found, according to some WTiters, in the free nitrogen 

 of the atmosphere ; but of any supply from this 

 source, other than the ready-formed nitrates con- 

 tained in rain, there is at present no substantial 

 proof. 



The Atmosphere as a Source of Plant- 

 food. — The combined nitrogen coming down in 



