3 



GARDENERS' MAGAZINE 



February 



8« 



Notes on Orchids. 



Paphiopedilum Chamberlainianum. 



This Sumatran orchid that has been well known for the last five or six years 

 is figured in the current issue of the Bot. Mag., t 7,578. It is especially noticeable 

 by reason of its perennial raceme, which slowly elongates and produces flowers, 

 a pair often being open at the same period. The rounded dorsal sepal is bright 

 green, with a red-purple base and nerves ; it has waved and ciliate margins. The 

 petals are bright green, narrow, linear, margined with purple, and with purple 

 streaks on the green ground ; they are twisted at about half their length, the twist 

 commencing from above in one and from below in the other. The prominent lip 

 is rich rose-coloured, and specked with red. Messrs. Sander and Co., of St. 

 Albans, introduced the species, and it was named by Mr. James O'Brien in honour 

 of the Right Hon. J. Chamberlain, Secretary for the Colonies. The species 

 requires a stove temperature. 



ANGIUECUM SESQUIPEt>ALE. 



This popular orchid is not always managed with conspicuous success, but Mr. 

 G. Emery, gardener to T. H. Nash, Esq., Garland Hill, St. Paul's Cray, Kent, 

 seems to understand it perfectly. A photograph sent, though not suitable for 

 reproduction, represents a fine specimen carrying two spikes, one bearing four and 

 the other five of the large creamy-white long tailed flowers that invariably attract 

 attention. The winter-flowering form of this most celebrated of the orchids from 

 Madagascar is not very popular in town collections, as the flower buds are so often 

 damaged by fog. Outside the smoke radius, however, it develops its flowers to 

 perfection. 



EPIDENDRUM MEDUS/E. 



The accompanying illustration represents a fine specimen of the above orchid 

 — more generally known under the generic name of nanodes — grown at Oswald 

 House, Edinburgh, the proprietor of which, J. Buchanan, Esq., is an ardent lover 

 of this order of plants. Although the specimen figuied is well shown as regards 

 compactness and density of foliage, yet it does not do justice to the size. There are 



Specimen 



OF EPIDENDRUM MEDUM2, GROWN AT OSWALD HOUSE, 



Edinburgh. 



foliare waft'a^n ftV™ iSP* V tW ° ^ et S ^ &ie > and if a measurement of ih 

 !!. £ he y must q u "e two feet six inches or more across ; indeed 

 they are sad to be hardly equalled in the kingd 



cimhlp cMnW*» u „_ *v' w „.„ &u om. air Wood, the energetic and 



gular plant by division, and the 



KSIS £ ma , de UP u b,ds fair to rival or °«tstrip the original in point of size 

 t£ \ !? 6 f l ! lture . bestow ed on these plants, the position they Scupy s one 

 SVt d f ventilator m a small span-roofed greenhouse, where floweringVants 



Tnd thev P Tat S ' a n y H CinthS ' **> ™ ^ d flowered at ^sea^on 



la"or is LmSt LninH eS ^ g °° d of Water overhead, wh.le the venti- 



have alwarten fonnH y .° Pen ' eXC ?* du ' ing frOStV Weather " Here the «Pecimens 



when „ flowS thT "T my u-^™ 1 visits durin * the few W and 

 when in flower they are always objects of interest and good cultivation This 



E^fr^r ^ intr ° duCed ^ Mr ' Backhouse, of Y^rk-R. L. Harrow^ 



Cattleya aurea. 



thJ a« a^JLS S °rj ab,e M C. Trian*, C. Mossi*, or C. labiata, but 



and Co seem & ? d ^ StmC i forms fairlv wel1 known - Messrs. Linden 



vSJwi • T- ho ^ ever ' to 'have obtained an importation showing considerable 



beek establishment „ d , escnbed ' ■» of them having flowered at the Moorte- 



same colour over a gSdwor^ of £ T^f P"^^ an d stripes of the 

 edged with rose ; petalTe'il , £2?E£ ti^*Wl&J*# is 



belt of red nnrrT \ X^f.. mg Cn ™ son P ur P le ^P^g int ° a broad central 



T 



PROCESS OF DE 



The subject of denitrification has, Professor R War,;., * 

 the current issue of the /ournat 'of the Royal A^SSK.J-R.S., ,,. 



broad sepals and petals being col o3 *^ * °' n****** . Very distinct ' its 

 whole centre and apex bdnf Sfcl J?^ T 5 S ' h ? 18 ver y dark > the 

 radiating vein-like into the suLundTn? Si ^ CnmS ° n ' tWs CO,OUr 



that a great deal of the work done has been already forS 



C. a. musaica seems well 

 rgined laterally with rose dotted 



with purple ; the apical margin is pal e 'yellow 1 " 



the central purple afd 3^^??, ^-^ed areas th 

 margin of the same colour. P ' 



(7. a. 



areas * 



apex is crimson purple, and the 



past thirty •Sr^mJ*--., 

 ignorance ot a tresn generation of worW AIld is now kZ5 



^ »»« mod* 



the earW 



belongs 



investigators. An historic il treatment of the subject would P £ Ce ^ 

 Prefacing, therefore, his remarks by saying that Dr. Angus SmSf ^r 1 ? un «ut*k 

 in 1867, was apparently the first to observe the destiSction ot \t Manch «te, 

 evolution of gas in decomposing organic solutions, he orocepHc \ ♦ ? tes ^ the 

 view of the facts connected with denitrification. F lu ^as to take agc^j 



The reduction of nitrates which occurs in solutions or soil 

 oxidisable organic matter is of several distinct kinds. The C °, ntai . nin g 'eidfly 

 ■ - . - ** * * * ' ' Auction may ^ 



organisms are destroyed in sewage or soil 

 mediums are sterilised 



latter b? 



simply from nitrate to nitrite ; or it may be from nitrate to nitric oil? 

 nitrous oxide gas ; or, finally, to nitrogen gas. The first form f 5 gas ; 0r • 

 not necessarily involve any loss pf nitrogen 5 all the others do " ^1 0Ti 

 nitrogen, as the product escapes in the form of gas. Evolve a loss of 



The reduction of nitrates is occasioned by various species of bacteria ■ 

 action m question only occurs in the presence of these living nrZ; ^ atlhe 

 established by Meusel (1875) in the case of natural ^ten^d S^t^^ 

 by Dehdrain and Maquenne (1882) to hold true in the^Ssd^^ 1 ^ 



• A . f -. c . ~ if > to use modern lanc^e !2 



R 1 ' a *t ? G mtn . ficat \ on nor denitrification will occur 8 ^ ^ 

 Bacteria reduce nitrates by bringing about the combustion of organic 



the oxygen of the nitrate, the temperature distinctly rising during the 10^' 

 When circumstances are favourable to the process of rediinhW X! °P eratl ». 

 nitrate re d„c=d is deterntijed b y the q^it? Z LtS 

 present The combustion of the organic matter, and reduction of the niL?^ 

 take place m the absence of air, in the same way as gunpowder^comrSd^ 

 nitrate, charcoal, and sulphur-is capable of burning under water Vi! 

 presence of air, the oxygen which it contains takes the place, more or less nf Z 

 oxygen of the nitrate, and the reduction of nitrate is either diminished' 0 2 

 oxidation of the organic matter much increased. The whole action is quite simfcr 

 to the familiar combustion of food in the animal body ; or to the combustiZ! 

 organic matter which occurs in plants, and notably in those which, as is the a* 

 with fungi, are destitute of chlorophyll. 1 m 



Different species of bacteria behave very differently in a mixture of a nitrite 

 and organic matter. Many species of bacteria are incapable of reducing a nitnta. 

 though quite capable of effecting the combustion of organic matter with fat 

 oxygen. The reduction of a nitrate to a nitrite, but not to the state of gas, k 

 however, a very common property of bacteria. Gayon and Dupedt (1866) wot 

 the first to isolate the species of bacteria reducing nitrates to gas ; two organbw 

 having this property were separated by them from sewage. Quite recently Bum' 

 and Stutzer (1895) have isolated denitrifying bacteria from horse dung, and fro* 

 straw. These organisms differ in several ways. The one obtained from straw is 

 capable of reducing nitrates to gas in the abserce of oxygen, and in the presence of 

 much oxygen its action is hindered, and finally ceases. The bacterium from hone 

 dung develops exclusively in the presence of oxygen, but it can reduce nitnto 

 only when associated with another organism of anaerobic character ; that is, ooe 

 developing in the absence of oxygen. When the two organisms are associated, do 

 reduction takes place in the complete absence of oxygen, but the action become* 

 active as soon as a little oxygen is present, and, when plenty of organic matter if 

 present, the process is apparently not hindered by a full supply of that gas. That 

 is no evidence that either straw or horse dung contains only, or always, the tit 

 denitrifying organisms just described. 



Soil contains an abundance of reducing organisms, including those producing 

 nitrogen gas. When broth containing one per cent, of nitre is infected with 1 

 particle of surface soil, and kept in a warm place, a quantity of gas bubbles con- 

 taining nitrogen is produced, and the nitrate will entirely disappear. Soil treated 

 with a one per cent, solution of sugar, containing nitre, rapidly reduces tk 

 latter ; the gas produced contains nitrous oxide and nitrogen. Any kind of 

 organic matter readily oxidised by bacteria may be used to bring about the 

 reduction of nitrates. In the trials made by various experimenters, albuminoid* 

 asparagine, starch, sugar, humus, fats, tartrates, citrates, acetates, and alcoW 

 have all proved effective for this purpose. The presence of some nitropMf 

 plant food, and of phosphates, potash, and the other ash constituents of plants, a 

 of course necessary for the growth and activity of the reducing bacteria. 



It is clear from what has gone before that denitrification may be expected » 

 occur whenever a suitable mixture of nitrate and organic matter is infected by a* 

 dust under the conditions favourable to the action. The early observations 0 

 Angus Smith in England, and of Th. Schloeaing in France (1868), taught us W 

 organic solution?, as sewage, diluted blood, tobacco juice, and sugar soluM* 

 when undergoing fermentation or putrefaction, actively reduced nitrates, n»* 

 oxide and nitrogen being evolved. Whence did these mixti 

 bacteria necessary for this action to take place ? Nothing had been done to n» 

 duce the organism ; indeed, at the date of these observations it was not 

 that the action was broughc about by bacteria. The answer is plain : these orgg 

 solutions obtained the organism which reduced nitrates by ordinary contact * 

 atmospheric air. 



Having grasped the facts now before us, we are disposed to smile when ^ 1 ? 



obtain 



equence 



use 



manure for soils. It is doubtless quite true, as we are informed by ^ 

 others, that rye-straw, olaced in Iwater containing saltpetre, slowly redu» ^ 

 nitrate present. But this result is not due to any peculiar property of stra . 



action 







matter contaminated with atmospheric dust had been made use of. ^ rt *! , ^ ie 

 experimenting in this way, has obtained similar results when using ^VJ^i 

 the straw of wheat, maize, or haricot bean ; lucerne silage ( c,}nsen * ? 

 or maize cake. That atmospheric contamination was the source of tne n - % 

 reducing nitrates which were present in these experiments is strikingly ew— • 

 the case ot the maize cake. 



It is assumed by the German experimenters that the solid £ 

 herbivorous animals, and especially that of the horse, is peculiarly ^ 

 «* M M»^_L_ ... ...^ of r anitrate to gas; the only founda*»JJ ^ 



the. marked oower of reducing nitrates P»^- 



these excrements. 



Wagner tells us that if a hundred grams of horse - , 



I rr™ ~C AAnhini'nff fivP PTamS of ^ U P^ fcj 4f* 



added to a thousand grams of water containing five grams 

 whole allowed to stand in a warm place, the nitrate will disappea. ^ ^ 

 the escape of gas being shown by a brisk effervescence of the ^1 

 hasty conclusions have been arrived at during the discussion 01 



