240 Encyclopaedia of Gardening 



Nicotiana, Tobacco (nicotia-na, after M. Nicot. Ord. Solana- 

 ceae). The genus Nicotiana is important economically because 

 from the leaves of the species Tabacum is prepared tobacco. It is 

 mot unimportant from the garden point of view, because it contains 

 several useful garden plants, notably alba, generally called affinis, 

 which produces sweet white flowers in abundance; Sanderae, a 

 plant of somewhat similar habit to the latter, but taller and with 

 rose or magenta flowers; and sylvestris, which grows 4 ft. high, 

 and bears white flowers. Alba and Sanderae are best treated as 

 iialf-hardy annuals (see Annuals). Sylvestris may be treated as a 

 .hardy perennial. Tomentosa (colossea) is sometimes grown for its 

 ^handsome foliage. 



Nierembergia (nierember-gia, after Sefior Nieremberg. Ord. 

 Solanaceae). The species gracilis is generally grown as a half- 

 .hardy annual (see Annuals) ; it has white flowers, streaked with 

 purple, in summer, and grows about 9 ins. high (see the Botanical 

 Magazine, t. 3108). It likes sandy loam and abundance of water. 

 Rivularis is a white-flowered creeper, suitable for pot culture or 

 moist parts of the rock garden (see the Bot. Mag., t. 5608). 



Nigella, Love-in-a-mist, Devil-in-the-bush (from niger, black, the 

 colour of the seeds. Ord. Ranunculaceae) . Pretty hardy annuals. 

 See Annuals and Love-in-a-mist. 



Nightshade. See Solanum. 



Nightsoil. Human excrement mixed with dry soil or ashes and 

 lime and laid up for a few weeks is a good fertiliser, and may be 

 .applied to soil for Green vegetables. See Manures. 



Nitrates. Free nitrogen is not available for plants, and cannot 

 benefit them until combined with a mineral to form a nitrate. 

 Nitrate of soda is a popular form. Nitrolim (calcium cyanamide), 

 rsulphate of ammonia, and nitrate of potash also yield nitrogen. See 

 Manures. 



Nitrification. The process by which non-available nitrogenous 

 matters are converted into compounds that can be taken up by the 

 roots of plants. The process is performed by bacteria, which 

 multiply the most freely in moist, warm, well-drained, friable soil. 

 The object of the gardener should therefore be to improve the 

 imechanical condition of his soil. 



Nitro-bacterine. A laboratory culture of the microbe Pseudo- 

 monas radicicola, which takes free nitrogen from the atmosphere 

 -and stores it in the form of nitrates in the root-nodules of leguminous 

 crops, such as Peas. Experiments conducted by the Royal Horti- 

 cultural Society throw grave doubts on the value of the preparation. 

 .See Manures. 



Norfolk Island Pine, Araucaria excelsa. 

 Norway Maple, Acer platanoides. 

 Norway Spruce, Picea excelsa. 



Nothoclaena, Gold and Silver Maidenhairs (nothoclae-na, from 

 mothus, spurious, and chlaina, cloak, from some appearing to have 



