MAN 



[ -517 J 



MAN 



MANU'LEA. (From manus, the hand ; 

 from a faint resemblance in the divisions 

 of the flower. Nat. ord., Fiyworts [Scro- 

 phulariacese]. Linn., Ik-Didynamia 2-An- 

 giospermia. Allied to Chsenostoma.) 



Greenhouse evergreens, from the Cape of Good 

 Hope. Several species are taken from this genus 

 and added to Lyperia. Seeds, sown in spring, in 

 a slight hotbed ; cuttings of the young shoots, 

 firm at their base, in sand, under a bell-glass, but 

 without bottom-heat ; sandy loam and peat, and 

 leaf-mould. Winter temp., 38 to 48. 

 M. cheira'nthus (wallflower). 1. Orange. August. 

 1/95. 



corda'ta (heart-teat^). . Red. July. 1816. 



ru'bra (red). l. Red. June. 1/90. 



visco'sa (clammy). 1. Pink. September. 1/74. 



MANURES are either animal, vegetable, 

 or mineral. They directly assist the growth 

 of plants, by entering into their compo- 

 sition, by absorbing and retaining mois- 

 ture from the atmosphere, by absorbing 

 tbe gases of the atmosphere, and by sti- 

 mulating the vascular system of the plants. 

 Manures indirectly assist vegetation, by 

 killing predatory vermin and weeds, by 

 promoting the decomposition of stubborn 

 organic remains in the soil, and by pro- 

 tecting plants from violent changes of 

 temperature. 



All these properties seldom, if ever, 

 occur in one species of manure ; but each 

 is usually particularized by possessing 

 one or more in a superior degree. That 

 is the most generally applicable manure 

 which is composed of matters essential 

 to the growth of plants: the chief of 

 these are carbon, hydrogen, and oxygen ; 

 therefore all animal and vegetable sub- 

 stances are excellent manures. It would 

 evidently be of great benefit if every 

 plant could be manured with the decaying 

 parts of its own species. This rule mighl 

 be so far followed as that the stems oi 

 potatoes, peas, &c., could be dug respect 

 ively into the compartments where those 

 crops are intended to be grown in th 

 following year; but such manure requires 

 the addition of ammoniacal salts. 



Some manures ameliorate a soil by ab 

 sorbing moisture from the atmosphere 

 This property is, at least, as beneficial to 

 ground that is aluminous as to that which 

 is siliceous ; for it is equally useless t< 

 either during periods of plentiful rain 

 but in the drought of summer, when 

 moisture is much wanting to plants, it i 

 beneficial to both ; in very dry seasons i 

 is even of greater importance to claye; 

 than to light soils ; for vegetation on th 

 former suffers more from long-continuei 



rought thtm on the latter, the surface of 

 he clayey soil becoming caked and im- 

 lervious to air, the only grand source of 

 ompensatory moisture that is available 

 o the languishing plants, and which is 

 nore open to those which grow on light, 

 and, consequently, more pervious soils. 



The following table of the comparative 



absorbent powers of many manures is 



xtracted chiefly from An Essay on the 



Use of Salt in Agriculture, by Mr. Cuth- 



>ert Johnson : 



Horse-dung evaporated previously to 

 Iryness, at a temperature of 100, ab- 

 orbed during an exposure of three hours 

 ,o air saturated with moisture at 62, 145 

 mrts ; putrefied tanners' bark, under 

 similar circumstances (66), 145 parts; 

 unputrefied tanners' bark, 115 parts ; cow- 

 lung, 130 parts; pig-dung, 120; sheep- 

 dung, 81; pigeon-dung, 50; refuse marine 

 salt (60), 49|; soot (68), 36; burnt 

 clay, 29 ; the richest soil (in one hour), 

 23 ; coal-ashes, 14; lime (part carbonate), 

 11 ; crushed rock-salt, 10 ; gypsum, 9 ; 

 lialk, 4. 



The absorbing power of a manure is 

 much influenced by the state in which it 

 is presented to the atmosphere. In a 

 finely-divided state mere capillary attrac- 

 tion assists it ; hence the importance of 

 keeping the soil frequently stirred by 

 hoeing, &c. But a mere mass of cotton, 

 by means of capillary attraction, will ab- 

 sorb moisture from the air ; yet it parts 

 with it at a very slight elevation of tem- 

 perature. It is of importance, therefore, 

 to ascertain which are the manures that 

 not only absorb but retain moisture 

 powerfully. The following results of our 

 experiments throw some light on this 

 point : 



Pig-dung evaporated to dryness at a 

 temperature of 106, and then moistened 

 with six parts of water, required for 

 being reduced to dryness again, at the 

 above temperature, 135 minutes ; horse- 

 dung under similar circumstances, 90; 

 common salt, 75 ; soot, 75 ; rich soil, 32 ; 

 chalk, 29 ; poor soil (siliceous), 23 ; gyp- 

 sum, 18. 



These experiments point oat a criterion 

 by which we easily ascertain the com- 

 parative richness of any two given soils 

 or manures : the most fertile will be 

 most absorbent and retentive. 



Some manures increase the growth and 

 vigour of plants by stimulating their 

 absorbent and assimilating organs. Tu* 



