118 THE VICTORIAN NATURALIST. 



Till showers and snows the subtle atoms swell, 

 And spread the enduring foliage ; then we trace 

 The freckled flower upon the flinty base ; 

 • These all increase, till in unnoted years 



The stony tower as gray with age appears, 



With coats of vegetation thinly spread, 



Coat above coat, the living with the dead. 



These then dissolve to dust, and make a way 



For bolder foliage, nursed by their decay : 



The long-enduring ferns in time will all 



Die and depose their dust upon the wall : 



Where the winged seed may rest, till many a flower 



Shows Flora's triumph o'er the fallen tower." 



Following out this theory of mutual help between plants, we 

 find that it is not only in connection with lichens that the hyphse 

 of fungi take an active part, but that many of our flowering 

 plants — aye, some of our largest trees — do not disdain to enter 

 mto partnership with them. 



The usual mode by which plants obtain nourishment is by the 

 action of tiny cylindrical outgrowths from the outermost layer 

 of cells which surrounds the smaller rootlets. These outgrowths 

 are called root-hairs, and they absorb the moisture from the 

 surrounding soil. This moisture holds certain salts and other 

 minerals in solution, which are essential to make up cell sap. 

 The sap ascends through the roots and stem until it arrives at 

 the leaves, and here it is converted into an organic substance by 

 the assimilation of carbon, which the leaves obtain from the 

 atmosphere. The organic substance thus obtained, and which 

 is termed elaborated sap, passes from the leaves into special cells 

 and vessels in the stem, and is finally brought into contact with 

 every minute portion of the plant. 



Here we see that it is necessary to have two sets of organs — 

 one to provide the water and food-stuffs from the ground, and 

 the other to obtain organic matter from the air. 



It is well known that many plants, such as Roses, Ivy, and 

 Pinks, can be easily propagated by placing slips in pure damp 

 sand ; on the other hand, if slips of Oak, Broom, Heath, or 

 Rhododendrons be placed in such sand, they may strike root, but 

 no further progress will be made. If, however, the sand be 

 mixed with soil taken from heathy, or forest land, the plants will 

 thrive. These facts roused the curiosity of botanists, and it was 

 found that the heathy and forest soil was thickly intermingled 

 with the hyphae of fungi. Further experiments showed that the 

 younger fibres of the roots of Broom, Oak, Birch, Spurge-Laurel, 

 and more particularly heath plants, as Erica and Epacris, were 

 completely surrounded by a felted coat of hyphae, also that very 

 few or no root-hairs were found on some of these plants : whereas 

 the hyphse not only enveloped, but actually pierced the outside 

 cells of the roots, and their other ends straggled far and wide into 



