524 On the Roots differing in each Soil. 



As to the tree and shrub, they are certainly more indebted to 

 the root than to the atmosphere, though a quantity of nutri- 

 ment is also received by the leaves. It is known tliat in many 

 trees the roots almost eciual in extent the spreading branches ; 

 and as each of the side limbs below^ ha-s such a set of branches 

 to support above, they must of course increase with their leafy 

 honours. It is the side roots which bring the greatest quantity 

 of sap: they often reach an immense way; and as the radicles 

 placed in the whole extent are mostly turned upwards, it is in 

 great part the produce of that vegetable matter lying near the 

 surface Avhich bestows on them its richest juices. A large num- 

 ber of circular vessels in the middle of these roots convey these 

 treasures to the centre root, while the rest (adjoining the bark), 

 are filled with fresh-forming seeds. Trees and shrubs as well as 

 luscieus plants (see fig. 9) have all the assistance the radicula, as 

 well as fibres and hairs, can bestow on them ; but many have 

 also those balls of fat matter which adhere often to the sides of 

 the fibres, and must add much to the nutriment of the plant. 

 But when it is a fir or an ever-green tree. Nature has still another 

 resource. Dissecting many roots of firs, 1 discovered in the balm 

 of Gilead fir, at the termination of each side root, a large bun- 

 dle of radicula; it had a most strange appearance ; nor could I 

 at first understand its use, till I examined it thoroughly, and 

 found it was to increase the nourishment within a given distance. 

 To give an idea of the contrivance, I subjoin the specimen; it is 

 however scarce one quarter of it, see fig. 5. Besides this, the 

 tree had fibres, hairs, and halls; it must therefore have had be- 

 stowed on it ample amends for the nutriment it lost in its leaves. 

 In the rich loams, and those plants which are only suited to 

 them, the quantity of roots is prodigious ; 1 have often seen 

 them twice the size of the plant, for example the rape plant, 

 see fig. 9, which draws much juice from the earth. The bog 

 plants also have m.any spreading roots, and arc extremely in- 

 debted to the soil for support. 



But I must not pass over the curious form of the roots of the 

 water plants. They hang like a syphon in a straight line from the 

 middle root, making' first a sort of cun^e like that instrument, 

 see fig. 6 : by this means, and by a managed vacuum above, they 

 draw up the water to the plant, as the impervious skin round 

 tlie root will not permit it to enter in any other way, though 

 growing in or on the water : the stem of the leaves serves to toni- 

 municate the air at the first return of light ; and when this is 

 drawn off by the wants of the plant, it completes the vacuum, 

 which draws up t'le water in the hanging routs, which had been 

 closed by cold and darkness, and re-opened by light and air. If 

 the roots are taken out of tlie water at night, they will always be 



lomid 



