554 
THE DICTIONARY OF GARDENING, 
NIPHZA. Eight species are now referred to this 
genus. To those described on. p. 453, Vol. Il, the 
following should be added: 
N. Roezlii (Roezl’s). fl. small, in the upper axils, on long, 
glandular-hairy, purple pedicels. J, stalked, 1sin. to 24in. long, 
ovate, obtuse, crenate, rugose, dark green. Tropical America. 
Plant dwarf, compact, covered with white or reddish hairs. 
(R. G., t. 896.) 
N. rubida is the correct name of Phinwa rubida. 
NITRATES. See Nitrification. 
NITRIFICATION. Nitrification has an important 
bearing upon horticulture. Nitrogen in the form of 
nitrates is generally regarded as the best kind of nitro- 
genous food for plants of all descriptions. Nitrates are 
compounds of nitric acid with mineral bases, as potassium 
nitrate, sodium nitrate, caleinm nitrate, and ammonium 
nitrate. Plants obtain their nitric acid by absorbing the 
nitrates that are already present in the soil—those that 
are carried down to the soil from the atmosphere in 
rain, dew, hoar-frost, and snow; those that are applied 
artificially in fertilisers; and those that are formed in the 
soil from the nitrogen of other substances. 
As is well known,-all the nitrogen that is applied to 
the soil for fertilising purposes, especially in farmyard 
and stable manures, compost heaps, in green-manuring, 
and by animal manures, is not in the form of nitrates. 
It may be either in the form of ammonia or of more 
complex organic compounds. It is very probable, 
however, that before it is taken up by the growing 
plant the organic nitrogen is changed, first into the form 
of ammonia, and then into nitric acid. 
These changes all take place through the agency of 
micro-organisms, or ferments, in the soil, and that 
particular process in which the nitrogen of the ammonia 
is changed into nitric acid is called Nitrification. This 
change is accomplished by the joint action of two 
separate organisms, one of which changes the nitrogen 
of ammonia into nitrous acid, while the other changes 
the nitrous acid into nitric acid, the latter being the 
form in which it is assimilated by plants. 
The conditions that are required for the development 
of nitrifying organisms are the presence in the soil of 
certain food-constituents—heat, moisture, oxygen, and 
some mineral base—to neutralise the nitric acid as it 
is formed. It is also necessary that the soil be slightly 
alkaline. _The nitrifying organisms require certain 
substances as food, among which phosphorie acid and 
lime are most important. It has been found that with- 
out phosphoric acid there can be no Nitrification. This 
probably is one of the reasons why phosphatic manures 
show such beneficial results when applied to certain soils, 
as well as furnishing direct plant-food. 
The three conditions which exert a marked influence on 
Nitrification, and which in horticultural practice are 
more or less intimately associated, are heat, air, and 
moisture. The process is most rapid during warm 
weather, in presence of sufficient air and moisture. 
Hence it is more active in summer than in winter, and 
more rapid in a conservatory or covered frame than in 
the open garden. 
Nitrification also teaches the gardener the reason why 
thorough tillage of the soil is so essential, and why 
charcoal, added to potting material and a sufficiency of 
drainage crocks, in pot culture, is so important and 
beneficial. The loosening and pulverising of the soil allow 
the admission of the necessary -oxygen, and regulates 
the supply of moisture. If the soil is allowed to become 
very dry, or, on the other hand, is saturated with water 
to the exclusion of air, Nitrification is retarded, and may 
be permanently stopped. In this connection it is interesting 
to note that in certain plant-cultures, especially that of 
the Chrysanthemum, if the soil is allowed to get thoroughly 
dry, the plants never afterwards seem to regain their 
former healthy vigour, nor will they produce such fine 
blossoms as if a steady and continuous growth is 
maintained. 
The final product of Nitrification is nitric acid; but 
the nitrifying organisms cannot develop in the presence 
of a free acid; hence the benefit of liming sonr soils, 
such as water-meadows, peaty soils, or very rich old 
garden soils. The lime corrects the sourness of the soil 
by neutralising the free acid, and then, if the other 
conditions of heat, oxygen, moisture, and food are 
favourable, Nitrification may proceed. There must be an 
Nitrification—continued. 
excess of lime applied over and aboye the amonnt 
necessary to correct the acidity of the soil in order to 
neutralise the nitric acid as it is formed. 
Whenever the soil is in a condition unfavourable to 
Nitrification, there is danger that not only may nitrates 
not be formed, but that there will be a loss of nitrogen 
from those nitrates which are present. This loss is due 
to a process known as Denitrification (which see). 
NOCCZZA (named in honour of Domenico Nocea, 
Professor of Botany at Pavia at the end of the eighteenth 
century). Orv. Crucifere. A genus embracing only 
two species of small, hardy, European herbs, allied 
to Iberis. Flowers white or lilac, sub-corymbose, bract- 
less; sepals spreading; petals entire; scapes naked. 
Radical leaves crowded, pinnatisect. Only one of the 
species has been introduced. For culture, see Biennials. 
N. stylosa (large-styled). . pale lilac; stamens, petals, and 
style about equal in length. J. slightly fleshy ; ies ones 
pends obovate-oblong, nearly entire; upper ones alternate, 
lanceolate, 14in. long. h. 4in. South Europe, 1879. Biennial. 
Syn. Jberis stylosa (R. G., t. 1029, f. 3). 
NOHL-KOHL. ‘ee Kohl-Rabi. 
NOLANA ROSTRATA. A synonym of Osteo- 
carpus rostratus (which see). 
NOLI-ME-TANGERE. See Impatiens Noli-me- 
tangere. 
NOLINA. See also Beaucarnea. 
NOLTEA AFRICANA. This is the correct name 
of the plant described on p. 209, Vol. IV., as Wille- 
metia africana (which see). 
NONE-SO-PRETTY. Sce Saxifraga umbrosa. 
NORDMANNIA CORDIFOLIA. A synonym of 
Trachystemon orientalis (which sce). 
NORMANDY CRESS. Another name for American 
or Land Cress (which see under Cress). 
NORTENIA. A synonym of Torenia (which see). 
NOTHOCHLZENA. Gold and Silver Maidenhairs. 
Some of the members of this genus require stove 
temperature all the year round, while others sneceed best 
under greenhouse treatment. In that respect they are 
like Gymnogrammes and Cheilanthes, which, on account 
of either the woolly or the golden or silvery nature of 
the under-side of their foliage, they also resemble in 
general appearance. Most of the plants belonging to this 
genus are of a somewhat delicate nature, requiring more 
than usnal care, especially during the winter, to preserve 
their foliage, which, from its constitution, in many cases 
possesses the property of retaining moisture, and is there- 
fore apt to decay. An important fact to notice is that, 
from whatever part of the globe they come, all the 
Nothochlenas are invariably found on rocks much exposed 
to the sun, but so situated that the plants get a good 
supply of moisture at the roots. The majority of the 
species are of erect or semi-erect habit, although a few are 
particularly well adapted for growing in baskets of small 
or medium dimensions, in which they display their elegant 
fronds to advantage. In any case they should not be 
kept in a close or a moist place, a somewhat airy situation 
being indispensable to all of them. If grown in pots, a 
mixture of good fibrous peat and small pieces of sand- 
stone in about equal proportions is all that is required ; but 
great care must be taken to ensure perfect drainage, as 
stagnant water at the roots is highly injurious. Finely- 
sifted soil shonld be carefully avoided, as also should 
overhead syringings. 
Nothochlenas are almost invariably propagated from 
spores, which in some cases germinate freely ; but many of 
the species may also be increased by division of the crowns, 
which operation is best performed from March to May. 
Though considered somewhat difficult to manage, 
N. levis is one of those plants which amply repay any 
extra care bestowed upon them. Whoever has ee the 
good fortune of seeing it grown, as it was a few years 
ago, in the select collection of the late Mr. 8. Rucker, 
where, under Mr. Pilcher’s care, it formed a most 
handsome basket—the admiration of every visitor—will 
testify to the possibility of success. It only requires 
cool, or at the most intermediate, temperature and a dry 
position, such as a hanging-basket; and when grown in 
