88 DECOMPOSITION OF PLANTS. 



accomplished by the agency principally of other ani- 

 mals, or animated creatures ; so, in the vegetable world, 

 vegetating substances usually effect the entire decom- 

 position : for though, in the larger kinds, the high and 

 lofty ones of the forest, insects are often the primary 

 agents, yet other minute substances are commonly found 

 to accelerate or complete the dissolution. Fungi in 

 general, particularly those arranged as sphaeria, trichia, 

 peziza, and boletus, appear as the principal and most 

 numerous agents, and we find them almost universally 

 on substances in a certain state of decay, or approxi- 

 mation to it; though there are a few genera of this 

 class which are attached to, and flourish on, living ve- 

 getation. The primary decline is possibly occasioned 

 by putrescence of the sap, or defective circulation, and 

 this unhealthy state of the plant affording the suitable 

 soil for the germination of the parasitic fungus; for 

 there must be an original though inert seed, till these 

 circumstances vivify its principle. By what means the 

 parasite finishes the dissolution is not quite obvious; 

 but of that insidious race the byssi, of which family is 

 the dry-rot (byssus septica), the radicals penetrate like 

 the finest hairs into the substance, and thus destroy the 

 cohesion of the fibres. So do the nidularise, many of 

 the agarics, the boleti, and others ; and it is not unlike- 

 ly that this operation is the general principle of action 

 of the whole race, though not so obvious in the minuter 

 kinds. These terminators, many of which present but 

 little character to the naked eye, under the microscope 

 we find to be of various forms, though not always so 

 distinguishable from each other as the flowers of our 

 garden. Some of the genera of plants appear to have 

 distinct agents assigned to them, and the detection and 

 enumeration of them have been carried to considerable 

 extent by some of the foreign naturalists ; but, to point 

 out the variety and curious organization of these sub- 

 stances, we will only instance four, to be found on the 

 common plants of the garden or the copse : the laurel, 

 the elm, the sycamore, and the beech. 



The laurel (primus laurocerasus) is not, properly 

 speaking, a deciduous plant, though it casts its leaves 



