PAPILIONACEOUS PLANTS. 



PARING AND BURNING. 



celebrated Cherimoyer (Anona cherimnlia) found 

 in perfection in Mexico, Peru, and Brazil; the 

 Alligator pear (A. paluslris}, the Street sop (A. 

 squamosa), all esteemed West India fruits, about 

 as large as a middle-sized apple, and filled 

 with a soft, rich, delicious pulp. 



PAPILIONACEOUS PLANTS include 

 many of the most common and valuable plants 

 supplying food to man and animals, such as 

 pulse, beans, peas, tares, sainfoin, &c. The 

 papilionacoe take the name from the resem- 

 blance borne by their flowers to the butterfly, 

 as is seen in the blossom of the common pea. 

 The fruit forms a pod called a legume, and 

 such plants are hence named leguminous. 



PARASITICAL PLANTS are those which 

 grow into the tissue of other species, and feed 

 upon their juices. Of this kind are the mis- 

 seltoe, the broom-rape (Orobanche), the Lathreea, 

 &c. Such species have no proper roots. The 

 term parasitical is, however, often applied to 

 mosses, Orchidaceous plants, Tillandsias and 

 the like, which are mostly epiphytes, growing 

 upon the bark of trees, but deriving their food 

 from the air, by means of their own roots. 



PARING AND BURNING. This well- 

 known operation of agriculture, once much 

 more extensively practised in England than at 

 present, consists in paring off the turf to a 

 depth of two or three inches, generally with 

 a breast-plough worked by a labourer, or by a 

 turf-paring plough drawn by a horse ; allowing 

 it to dry, and then burning it in heaps. It is 

 commonly best performed in the months of 

 April and May. It is a practice now rarely 

 adopted on sandy or calcareous soils, although 

 productive of good results on peat, and some 

 kind of clay soil; but even there it is very 

 doubtful whether it is the best mode of treat- 

 ing the land. 



The practice is certainly as old as the days 

 of Virgil, who mentions it in the first book of 

 the Georgics. Endless have been the theories 

 brought forward to account for its operation. 

 Dr. Home thought it dispelled "a sour juice" 

 from the land. (Prin. of Agr.) Dr. Darwin 

 considered it produced "a nitrous salt" in the 

 ashes. " Many such obscure causes," says 

 Davy, " have been referred to for the purpose 

 of explaining the effects of paring and burning, 

 but I believe they may be referred entirely to 

 the diminution of the coherence and tenacity 

 of clays, and to the destruction of inert and 

 useless vegetable matter, and its conversion 

 into a manure. All soils that contain too 

 much dead vegetable fibre, and which conse- 

 quently lose from one-third to one-half of their 

 weight by incineration, and all such as contain 

 their earthy constituents in an impalpable state 

 of division, such as the stiff clays and marls, 

 are improved by burning; but in coarse sands, 

 or rich soils, containing a great mixture of the 

 earths, and in all cases in which the texture is 

 already sufficiently loose, or the organizable 

 matter sufficiently soluble, the process of torri- 

 faction cannot be useful. All pure silicious 

 sands," adds Davy, "must be injured by it;" 

 and here practice is found to accord with 

 theory. Arthur Young found "burning injured 

 Band;" and an intelligent farmer in Mount's 



Bay told me that he had pared and burned a 

 small field, several years ago, which he had 

 not been able to bring again into good con- 

 i dition. I examined the spot ; the grass was 

 very poor and scanty, and the soil a silicious 

 sand. 



The process of paring and burning, therefore, 

 seems to be most adapted for peaty or clay 

 lands ; for, as Davy continues, " the process 

 of burning renders the soil less compact, less 

 tenacious and retentive of moisture ; and when 

 properly applied, may convert a matter that 

 was stilT, damp, an'l in consequence cold, into 

 one powdery, dry, and warm, and much more 

 proper as a bed for vegetable life." 



Davy examined three specimens of the ashes 

 from different lands that had undergone paring 

 and burning. (See ASHES, ante, p. 115.) "The 

 great objection," he adds, " to this operation is 

 that it destroys vegetable and animal matter, or 

 the manure in the soil : but in cases in which 

 the texture of its earthy ingredients is perma- 

 nently improved, there is more than a compen- 

 sation for this temporary disadvantage. And 

 in some soils where there is an excess of inert 

 vegetable matter, the destruction of it must be 

 beneficial ; and the carbonaceous matter re- 

 maining in the ashes may be more useful to 

 the crop than the vegetable fibre from which it 

 was produced." (Agr. Chein. p. 344.) 



Liebig thinks that all the benefit of burning 

 the soil is attributable to its thus obtaining in- 

 creased powers for the absorption of ammonia. 

 He says, " Soils which contain oxides of iron, 

 and burned clay, must absorb ammonia, which 

 is favoured by their porous condition ; they 

 further prevent the escape of the ammonia 

 once absorbed by their chemical properties. 

 The ammonia absorbed by the clay, or ferru- 

 ginous oxides, is separated by every shower of 

 rain, and conveyed in solution to the soil. 

 Powdered charcoal possesses a similar action, 

 but surpasses all other substances in the power 

 which it possesses of condensing ammonia 

 within its pores, particularly when it has been 

 previously heated to redness. Charcoal absorbs 

 ninety limes its volume of ammoniacal gas, 

 which maybe again separated by simply mois- 

 tening it with water." (Organic Chem.) 



And it is evident, from the experiments 

 which Liebig gives, that charcoal powder is a 

 very fertilizing application to some plants. 

 The practice, however, of paring and burning 

 is evidently one whose advantages the farmer 

 and the chemist admit with reluctance. And 

 it is very probable, that by other means, such 

 as the use of lime, &c., most soils may be 

 cultivated with more advantage to the farmer 

 by the avoidance of this expensive and de- 

 structive process. "My practice," remarks 

 Mr. Pearson, "in the use of turf for various 

 purposes, convinces me that all lands must be 

 injured by paring and burning, save those 

 lands, which are few and far between, that 

 possess too much inert vegetable matter; or, 

 in other words, lands that grow their crops to 

 such a state of luxuriance, as to prevent the 

 desired intent of the cultivator. Those lands 

 which possess too much inert vegetable matter 

 ; might also be improved by having part of their 



871 



