The Science of the Soil 



95 



(e.g. Oaks, Beeches, Poplars, Elms, Rhododendrons, Cranberries, Bilberries, 

 Brooms, Heaths, Conifers, &c.) are invested with the filaments of certain 

 fungi, which, instead of being injurious, are actually beneficial. These 

 fungal threads are interwoven in the tissues of the feeding roots, and often 

 look like root hairs, and perform similar functions of absorbing water from 

 the soil together with the mineral salts and other compounds dissolved 

 in it. The name of " mycorniza" has been given to these fungi which 

 envelop the roots of many plants, and it has been proved that they are 

 not only beneficial and essential to the plants on which they grow, but 

 that they can only come into existence when humus is present in the soil. 

 This accounts for the great esteem in which all gardeners hold leaf mould 



Fig. 83. 1, Roots of White Poplar with inycelial mantle. 2, Tip of Root of Beech with closely 

 adherent mycelial mantle x 100 (after Frank). 3, Section through a piece of wood of the White Poplar 

 with the mycelium entering into the external cells, x 180. 



as an ingredient in the soils they use, and they know by actual experience 

 that a soil without humus or leaf mould would be practically useless for 

 their plants (fig. 83). 



Chemically, humus gives rise to living micro-organisms in the soil, 

 when lime is present, during the process of fermentation and decay, if 

 the temperature is favourable, .and thus yields up a supply of organic 

 food in the process of decomposition. 



The following table shows the composition of three different kinds 

 of humus: 



