VEGETATION. 



niulated in grafs lands as much as pofiible ; but where grain- 

 crops are to be raifed, a proper mixture of other earths 

 IS neceffary, to give them llabihty, and prevent their being 

 thrown out of the ground. 



Vegetable Fly, in Natural Hlftory, an infeft found in the 

 ifland of Dominica, and (excepting that it has no wings) re- 

 fembling the drone in fize and colour. In the month of 

 May this infeft buries itfelf in the earth, and begins to 

 vegetate. By the latter end of July the tree is arrived at 

 its full growth, and refembles a coral branch ; being about 

 three inches high, and bearing fcveral little pods, which 

 dropping off become worms, and afterwards flies, hke the 

 Enghfh caterpillar. Dr. Hill, in his account of this pro- 

 duftion, to whofe examination it was fubmitted, obferves, 

 that the cicada is common in Martinique, and in its nympha 

 ftate, in which the old authors called it fettigometra ; it buries 

 itfelf under dead leaves to wait its change ; but when the 

 feafon is unfavourable, many perifti : and that the feeds of 

 the clavaria JoboUfera, which is a fungus producing foboles 

 or fhoots from its fides, and growing in putrid animal bodies, 

 find a proper bed on this dead infeA, and grow. This, he 

 fays, is the faft ; though the untaught inhabitants fuppofe a 

 fly to vegetate, although there exifts a Spanifli drawing 

 of the plant's growing into a trifohate tree ; and it has been 

 figured with the creature flying with this tree upon its 

 back. Phil. Tranf. vol. liii. p. 270, &c. 



Vegetable Oil. See Oil. 



VEGETATION, in Fegetable Phyfiology. See Ger- 

 mination, Circulation of Sap, Spiral Vejfeh, Leaf, 

 &c. 



Vegetation, as it relates to Agriculture and Gardening, 

 is of confiderable importance, by explaining the nature and 

 means by which plants and crops receive nouriftiment and 

 fupport, and are the beft promoted in their different growths. 

 In refpeft to grain, feeds, and fets, it feems evident, from the 

 experimental enquiries of Mr. Gough and others, that during 

 the aft or procefs of their germination or infant vegetation, 

 they draw the oxygene principle from the furrounding atmo- 

 fphere, part of which is retained, and the remainder thrown 

 off, charged with a portion of carbon ; and that, in this pro- 

 cefs or operation, the fubftances of the feed-lobes, or other 

 parts that anfwcr the fame purpofe, of courfe undergo a con- 

 fiderable change, an additional proportion of the fame prin- 

 ciple entering into their compofition, while a portion of their 

 carbon is diffipated and deftroyed : that by this alteration in 

 the proportion of their conftituent principles and parts, the 

 faccharine fermentr.tion is induced to take place, and fugar is 

 formed, as demonitrated in the operation of malting grain : 

 and that the fugar and carbonic acid, from their being more 

 foluble in water than in the oxyd of farinaceous matter, 

 eafily combine with the moifture in the capillary vefTels of 

 the feed or other fubftances, and find a ready palTage to the 

 germ ; the vegetative principle being thu9 brought into 

 adtion by a ftimulus fuited to the particular natiu-e of it : 

 and that by the decompofition of the feed-lobes, or other 

 parts, a nutritious fluid being thus formed and difl:ributed 

 through the infant plant, its organs are excited to exert 

 their pecuhar fpecific aftions in decompounding the nou- 

 rifhment conveyed to them, and in forming new oxyds from 

 the elementary principles of it, in order to the increafe and 

 evolution of the vefTels and fibres. 



As it is in this manner that the firft ftage of germination 

 or vegetation is fnppofed to commence, it would appear 

 that in fuch feeds and fets, in order to their undergoing 

 thefe different changes the moft readily, and in the moft per- 

 feft manner, on which, p'-obably, healthy growth may ma- 

 terially depend, they fhould not only be properly depofited 



in the earth or foil, but, in the cafe of grain and feeds, be 

 fo well ripened and filled with farinaceous or mealy matter, 

 and poffefs fiich a degree of moifture, as may difpofe them 

 to undergo fuch changes in a fuitably fpeedy manner ; 

 while, at the fame time, a due fupply of proper nutritious 

 matter is afforded for the perfect germination and early- 

 growth of the infant vegetables or plants. They fhould 

 not confequently be put fo deep in the ground as to be too 

 much excluded from the aftion of the air, or be fown or 

 fet when in too dry a condition from the ftate of the feafon 

 or other caufes, but be conftantly fuffered to have as much 

 of the agency and influence of fuch forwarding powers as 

 may be neceffary for the perfeft vegetation and growth of 

 the plants or crops. 



Others conclude on the grounds, and for the reafons that 

 are ftated below, that two of the airs of which the atmo- 

 fphere is compounded, are abfolutely neceffary to the nou^ 

 rifhment and proper growth of vegetables ; thofe of vital 

 air or oxygen, and mephitic air or azote. It is found from 

 different trials, that plants placed in vital or oxygene air grow 

 larger, become more powerful, and are greener than thofe 

 put in that of the atmofpheric kind. That if the feeds of 

 the kidney-bean and the pea be put into earth of the fih- 

 ceous kind, and be fprinkled with water mixed with a fmall 

 portion of the oxygenated muriatic acid, in which oxygen 

 the moft abounds and the mofl loofely adheres, they ger- 

 minate much fooner than if fprinkled with pure water : but 

 that if feeds be immerfed in diluted muriatic acid, they be- 

 come black and rugous, and never germinate. That in no 

 kind of air deprived of oxygen do plants vegetate ; for 

 if they be placed in azotic or mephitic air, in carbonic or 

 fixed air, they become flaccid and drooping, it is faid, by 

 the heat of the fun, and gradually die away. And that in 

 nitrous air, plants become inaftive in a few hours. It would 

 appear from this, it is thought, that the portion of vital or 

 oxygene air imparts a natural ftimulus, which is highly ne- 

 ceffary to excite the fibres and fuftain the living power and 

 ftrength of the vefTels of plants ; and that, laftly, this air, 

 with the peculiar acidifiable bafes, generates the various 

 acids which are found in plants or vegetables. 



As the gluten of the fibres of vegetables confifts of car- 

 bon, chemically combined with azote, it follows, it is fup- 

 pofed, that the azotic air is abforbed or taken up by 

 the plants ; and that it is by this means that vegetables in- 

 creafe fo rapidly in rich foils, cemeteries, and other places 

 where animal and vegetable matters putrefy and decay in 

 large quantities in or on the ground. 



Carbonic air too diffolved in water is abfolutely ne- 

 ceffary to the vegetation of plants in order to provide their 

 carbonic principle, which is a conftituent part of the fibres, 

 oil, mucilage, and other vegetable principles. 



It 18 fuggefted, that plants appear to derive their caloric 

 or matter of heat from the furrounding atmofpheric air. 

 Hence it is that the fhades of trees are fo cool ; and that 

 nothing is more healthy for almoft all plants in their vegeta- 

 tion and growth, than mild tepid fhowers, by which they 

 obtain water together with this principle. That, lallly, feeds 

 do not vegetate in the cold, and many plants die in it. Heat 

 too IS evidently of much benefit in vegetation, as giving the 

 natural colour to the fohage, flowers, and fruits of plants, 

 caufing or promoting the flow and circulation of the fap- 

 juice, increafing the faccharine matter, and promoting the 

 flavour of moft forts of fruit. 



Light too contributes to the life and healthy growth of 

 plants ; for thofe which vegetate in atmofpheric air de- 

 prived of its hght, as in the night and dark places, become 

 pale and weak ; but in the day-time, ftrong and coloured. 



The 



