354 PRINCIPLES OF VEGETATION. 



Vegetables are greatly expofed to the depredations of infefts : almoft 

 every plant has numbers attached to itfelf, and many fiifFer by fcveral in 

 fucceflion j being while juft fprou ting the favourite food of fome, when 

 further advanced of others, and when mature of others. To this caufe 

 has been attributed the blight of corn. 



Vegetables, when decayed, compofe that kind of earth or mould, which 

 of all earths is belt adapted to nourifli vegetable life, and indeed with- 

 out which no fertility can be expefted. Hence, if in a fandy foil that 

 plant which can fupport fuch a foil be cultivated, and left to rot, then 

 another crop of the fame fucceed, and be ploughed in, by degrees the 

 fandy foil will become mixed with vegetable earth, and after a while 

 will be capable of nourifliing whatever plants are committed to its bo- 

 fom. 



Vegetation is no lefs ftrong in the water than on land ; in the ocean 

 than on the plains : nor is it confined to plants, but produces large trees 

 of folid wood. Of thefe we muft expect to continue ignorant, except 

 as accident difclofes them. Can thofe which grow in perpetual darknefs 

 be flimulated by light ? Have thofe variations of irritability which dwell 

 in a medium invariably cold and denfe, often perhaps ftagnant and mo- 

 tionlefs ? 



Thus we have endeavoured to illudrate the generation, growth, ftruc-. 

 ture, and nutrition of vegetables : their numbers forbid extending our 

 difquifitions, and their properties are various as their numbers; however, 

 ■we (hall juft obferve, that (omt zvQ'poifonouSy and in certain inftances fo 

 ftrongly as to poilbn the air around them. We have an extraordinary re- 

 lation of a great tree of this nature in Japan, to which only condemned 

 criminals are fent to gather its gum : they approach the tree to wind- 

 ward, yet few return to claim exemption from further punifhment. An- 

 other and a well authenticated inftance is the manchineel tree, undeu 

 whofe branches Ibould an unwary traveller take refuge, the drops of 

 rain falling from them Vy'ould at leaft corrode and blifter his fkin, if he 

 efcaped fo. Our own yew has fimilar, though very greatly inferior, re- 

 putation among fome. Nor fl:iould opium be forgotten, which is yielded 

 by the white poppy, cultivated for that purpofe in the Eaft: in fmall 

 quantities this promotes deep ; in large quantities fatal fleep. By habit 

 the Eaftern people can eat it in lumps, and drinking a glafs of cold 

 water after it, experience merely intoxication ; yet gradually it fhortens 

 their days, produces decrepitude, and undermines the natural powers. 

 The number of plants having poifonous qualities is confidcrable j and 



^ much 



