198 



Humus. 



Vol. X. 



genus is the cscidium. The cBcidium pine, 

 found on pine trees has, when magnified, 

 the appearance of a number of nine-pins. 

 When ripe it emits a bright orange coloured 

 powder. A mildew of this kind attacks bar- 

 ley, and is very injurious. It is vulgarly 

 called pepper brand. The Urego Segelum, 

 or smut, is destructive not only to barley, 

 but to wheat and oats. It destroys the grain, 

 which is converted into" a kind of jelly, and 

 attacks the leaves and stems. The puccinia 

 graminis which attacks corn, is formed in 

 the interior of the stock, and, when ripe, 

 bursts forth into clusters, like bunches of 

 grapes, of a dark brown colour. The ergol 

 on ry« is a well known and destructive spe- 

 cies of mildew. It grows out of a spike of 

 grain, like a prolonged kernel ; is long, hor- 

 ney, and cartilaginous. It originates in the 

 centre of the stem. It affects maize, and 

 various species of grass. 



"The principal fungi of the third class are 

 two, which attack the roots of plants, and 

 both resemble truffles. One of these {Rhi- 

 zoctonia Crocoruni) attacks crocuses. It is 

 called by the French Lamort du safran, and 

 soon destroys the whole crop. The other 

 fungus {Periola tomentosa) is found on the 

 potatoe, lucerne, &c. It turns the roots to 

 a purplish hue. They are both propagated 

 by spawn or fibres, which cling round the 

 roots. All these fungi propagate rapidly, 

 requiring only twenty-four hours to come to 

 maturity. One muslu'oom will propagate 

 250,000,000. Plants, Dr. L. says, are gene- 

 rally most affected by superficial fungi after 

 a long drought. Red plants are said to be 

 more liable to mildew than any other. Mr. 

 Bauer has found that steeping grains of corn 

 in lime water, will cure, or at least, prevent 

 the spread of the internal mildew. There 

 appears, however, as yet, to be no cure for 

 mildew in the roots, but by forming a deep 

 trench round the infected plants, and cutting 

 off all communication between them and the 

 rest of the field." 



Humus* 



The name usually given to this substance 

 is " mould." This term lias been misinter- 

 preted by many persons, who have under- 

 stood it to mean the layer of vegetable 

 earth, and not a particular portion of its 

 con.?tituenl parts. Several very clever ag- 

 ricultural writers have fallen into the same 

 error; and thus the obscurity which envel- 

 oped this part of the science has been in- 

 creased. It is on this account that I have 

 adopted the word humus, about which there 



can be no mistake. In a scientific point of 

 view tlie term "earth" is not at all applica- 

 ble to this substance; properly speaking it 

 is not an earth, and has only been called so 

 on account of the pulverulent form. 



Humus is always more or less a constitu- 

 ent part of the soil. The fertility of the 

 land depends entirely upon its presence, for, 

 if we e.\cept water, it is to this substance 

 alone in the soil that plants owe their nutri- 

 ment. It is the residue of animal and ve- 

 getable putrefaction, and is a black body; 

 when dry it is pulverulent, and when wet 

 I has a soft greasy feel. It is varied in its 

 I qualities and composition according to the 

 substances from wliich it has been formed, 

 and the circumstances Under v.'hicli,the pu- 

 trefaction or decomposition took place; there 

 are, however, certain properties which are 

 inherent to it, and in general it is similar in 

 itself. It is the produce of organic power — 

 a compound of carbon, hydrogen, nitrogen, 

 and oxygen, such as cannot be chemically 

 composed; for in inert bodies these sub- 

 stances only enter into simple combinations 

 of some two amongst them, and do not unite 

 altogether as is the case here. Besides the 

 four essential elements of humus, it contains 

 other substances in smaller quantities, viz., 

 phosphoric and sulphuric acids combined 

 with some base; and also earths, and some- 

 times different salts. 



Humus is the product of living matter, 

 and the source of it. It affords food to or- 

 ganization; without it nothing material could 

 have life, at least the most perfect animals 

 and plants could not exist; and, therefore, 

 death and destruction are necessary and ac- 

 ces.=ory to the reproduction of animal and 

 vegetable life. The greater the number of 

 living creatures, the more humus is pro- 

 duced, and, consequently, the supply of the 

 elements for the nutrition of life is increased. 

 Every organic being in life appropriates to 

 itself a daily increasing amount of the raw 

 materials of nature; and these, after having 

 been dige.sted, resolve into humus, which 

 increases in proportion as men, animals, and 

 vegetables are multiplied in any spot on the 

 surface of the earth. It is, however, dimin- 

 ished by the processes of vegetation, wasted 

 by being carried into the ocean by water, 

 and by being conveyed into the atmosphere 

 by the agency of the oxygen contained in 

 the air, which unites with and gradually 

 converts it into a gaseous matter. 



We have only to observe the progress of 

 vegetation upon naked rocks, in order to 

 understand the history of humus from the 

 very beginning of the world. At first, only 

 lichens and mosses are found there, from the 



