jANiuRY I, 1886.] THE TROPICAL AGRICULTURIST. 



507 



tlu'oughout their whole substance ; but they also letaiu 

 better stores of heat thus accumulatL'd thau chalky 

 marls do. 



If lime is preJomiuaut water is uot rea<fily absorbed. 

 The substance of the marl absoibs heat quicker be- 

 cause there is uo water to monopolise the lieafc for 

 itself; heat is th-LTefore easier imparted to 'Uailcj marl, 

 but.it also loses that heat more readily by radiation. 



Amongst tuo other minerals ihat eou.^titute the chief 

 iugredieuts of a good soil are potash and soda. They 

 are likewise derived from rociis. Their im]iortanoe 

 in agriculture will be discussed ou a later occatiou. 



Ordinary soil is chit fly composed of claj% lime, or 

 clay-lime (marl), sand (miuute particles of si'ica), 

 potash, and soda. There is tuother substance generally 

 Found in good soil which is uot of mineral origin but 

 which is a nioilihcation of carijou called humus. 



Humus is a suustance formed out of vegetable matter 

 in a stale of decomposition. Takmg a dead leaf as an 

 instance, we notice that its natural green colour 

 gradually changoo into yellow, from yellow into brown. 

 When dead leaves, chips, .«awdust, or other vegetable 

 olfal, are e.>;posed to the influence of the atmosphere, 

 thej gradually change into a dark brown substance 

 not uulike peat. In fact, peat is vegetable matter uot 

 perfectly decomposed. The beginning of the decay of 

 deail leaves, &c., is chiifly due to the influence of light, 

 moisture, and other atmospheric agencies. The process 

 of decomijositiou, however, is greatly promoted by 

 certam threadlike microscopic fungi called baotnviM. 

 How quickly decomposition will spread if the bacterise 

 have once got hold of vegetable substance is easily seen 

 in a case of iruit; if one apple or orange begins to decay 

 many others are also very quickly infected. During 

 this process of decomposition of vet,etable matter 

 several chemical changes take pkce, which, omng to 

 their subtle natm-e, we cannot well desciibe here. 

 Several acids are formed in succession — ulmic, humic, 

 crenic, apocrunic, and finally carbonic acid. This form- 

 ation of vegetable matter into carbonic acid gas aloue 

 is of great interest to the farmer. This process may go 

 ou very gradually, and humus, in its first state of 

 decomposition, may remain a long time in the soil before 

 the chemical changes to \vhich 1 have alluded actually 

 take place. Humus, when dry, is an earthy powdery mass 

 whicn does not dissolve in water, bat which absorbs it 

 readily, and forms a spongy muddy substance ; it grad-" 

 ually breaks up into a perfectly disintegrated state, 

 forming a soft mud which, alongwitli water, can be so 

 perfectly absorbed into clay or marl, and in such quant- 

 ities, that it serves as a store of vegetable food for 

 any plants that may grow on that soil in the course of 

 time. The several acids (ulniic, humic, crenic, ice. ) into 

 which humus successively changes have the remarkable 

 jjropprty of rendering soluble, in the water in which 

 they themselves are dissolved, mineral substances which 

 cannot be dissolved in ordinary water. These acids 

 facilitate thus the absorption of mineral matter by the 

 plants. Hunms is therefore not only vegetable food 

 for the young plant itself by being gradually changed 

 into carbonic acid, but it is the mediator for the diges- 

 tiou of mineral matter for the plant. 



There is another substance of interest to the farmer 

 which, however, we can in this place only briefly men- 

 tion. It is geiue. Like humus it is the result of de- 

 composition of vegetable matter, and it is found at the 

 bottom of ponds, lakes, and other stagnant waters. 

 ISrought into contact with carbonates, geine changes 

 iuto geinic acid, a substance which, owing to its corros- 

 ive nature, is highly detrimental to plants. Kxposcd 

 to the influence of the atmosphere, geinic acid grad- 

 ually changes into crenic and a pocreuic aeid.a snbject 

 to which further reference will be made on a later oc- 

 casion ; likewise to the substance called peat.— .J. S. 

 Herm.\ns fiCBiiiDi-.—Queenslandei: 



To PEEvtNi MusrAiiD-PLASTi.E from biioteiing, mix 

 with the white of an egg. — •boutkern I'fanltr. 



To Keep Inse.cts out of bird cages, tie up a little 

 sulphur iii a bag and suspend it in the e^ge. ifed 

 ants will neter ee roui.d iu a close' or drawer, if 

 a small bat,' of sulpiuir uc kept constantly in these 

 places. — Situtharn Planter. 



SIK WILijIAM HOOKER AND. KEW. 



The auuoHLC.-mem, that at the end of this month 

 Kew Gardens wiil be without a lloulter at their head 

 will be ruid nc-i only with regret, but with some- 

 thing apijroaching 10 consternation. Kew and Hooker, 

 Hooker and Kew, .vere, as it seemed, so hiseparaoly 

 combined tuat no severance coidd take place. If a 

 Hooker diu not plant the seed he tr,.nsierrr(l it 

 from the seed-bed and nurseil it till it bteame a 

 goodly trt^, while another Hoiker still further developed 

 the tree liil it bore abundantly jf flower and fruit 

 and see . lup'.aiucr t-srmi, Sir W'iUi&ni Hooker foimd 

 the g.:,-uen at its lowest ebb. Shortly lefore his 

 aoces.ijn to the office of L/irector, to such a state 

 of 8'.,_-naiiou hud the garden ai'rived that it was 

 seriously proposed to hand over the collections to 

 the Horiiicultural Society. In consequence of the 

 report .ind recommendation of the former Editor of 

 this journal, Sir Wihi.ini (then Dr.) Hooker removed 

 from Cila.sgow, where be had already done wonders 

 iu establishing and maintaining a botanical c:>rre- 

 spondencs and interchange of plants with all parts 

 of the world, and assumed the post of Director of 

 the iioyal Gardens, Kew. Those who remember the 

 okl state of things, speak of Hooker's transforming 

 touch as^ something magical. By his clear-hoadedness, 

 his uaCiring diligence and zeal, his extensive knowledge, 

 his stately courtesy, antl the encouragement he 

 extemled to all occupied in horticulture and botany, 

 he ri.ised Kew iu a very short time from its low 

 estate, and with the assistance of the ex-C'urator, 

 who still sm-vives, mide it the botanic garilen of 

 Euroi'B. Actually dyiug in harne-ss, at a ripe old 

 age, just twenty years ago, Sir William was succeeded 

 in the directorate by Dr. (now Sir Joseph) Hooker. 

 The career of the sou is well known, at least its 

 main features, to evei-y botanist, and to most gardaners. 

 His early travels iu the antarctic regions with Sir 

 tlames Koss, his adventurous wanderings in Sikkim 

 Himalaya, whence he introduced so many of the 

 glorious Khododendroiis, gave him fame, if uot fortune, 

 and on his return from India he occupied himself 

 with the determination and distribution of the ininionse 

 collections made by himself and Dr. Thomson, and 

 shortly after became Assistant-Director of the Gardens 

 under his father, so that on the decease of Sir 

 AVilliam in 1865 it was universally felt that he, and 

 he alone, was a fit successor. 



During the twenty years that have elapsed, the 

 record of Kew is one that the proudest admiustrator 

 might euvy ; the area has been greatly extended, 

 the succulent-house, the T-range, have been erected, 

 old houses have been removed, the herbaceous ground 

 remodelled, the frnticelum and rock garden con- 

 structed, the arboretum vastly extended, the museums 

 (three in number) greatly enlarged and improved, 

 the new herbarium built, the "North" gallery in- 

 stalled, the Laboratory erected. The two latter 

 establishments tistify to the confidence reposed iu 

 the Director. .Such mum'ficent gi:ts would never 

 have been made to the public had there not been 

 a general admiration of the admiiiistrativo ability 

 and competence of the Director, ^v bile all this new 

 work has been undertaken and carried to a succe.ssfnl 

 issue, -the maintenance and improvement of the old 

 have been such as to elicit admiration ; and herein 

 the chief has been well seconded by the Assistant- 

 Director, Mr. Dyer, Mr. John Smith (.vho occ.ipies 

 the same position that his namesake did under the 

 directorate of Sir AVilliam), and the othet otiicers 

 of the estabiishmeut. 



So far we have alluded to results which all e.=m 

 SCO for themselves, but ail the time that this work 

 of extension, supervision, .Tnd maintenance has be":n 

 going on, a vast amount of work nas been tlirowu 

 upon Sir Joseph, or rather he has himself developed 

 it in couuecliou with India and oi'.r colonies. 'J'he 

 father, Sir W'liiiani, early endeavoured to makf K'?w 

 the great ijuia'iical tcKtre of th >..i.g.isii-sptf.diiiig 

 world, and ILe hJea has beea f tliy devc^tp-fl by 

 the son. Kew U n".v the head centre of a lerias 

 of botanic gardens aiiU similar establishments through- 



