On the Natural History of Vegetables. 167 



terwards forming during induration interstices of various 

 figure and capacity for the same purpose. The various attach- 

 ments, contortions, and structure of this woody cylinder, are cu- 

 rious objects for the microscope ; and have been fertile sources 

 of conflicting opinions among men of science. Of this cylinder 

 the interior part next the pith is first formed, and is always 

 more compact in its texture than the exterior side or surface, 

 which has been recently, or is in the act of being, formed. 

 Third, the inner bark, which is visibly composed of longitudi- 

 nal fibres or threads, variously attached to each other ; and 

 when detached, presenting a kind of network similar to the 

 recent fibrils which insert themselves between two tiles, or 

 other smooth surfaces closely laid together. Fourth, the 

 bark ; the inner surface of which is partly composed of longi- 

 tudinal threads, resembling closely those of inner bark, and 

 from which there is no very distinct separation ; but its exte- 

 rior surface presents a very different structure, being composed 

 of parts both longitudinally and transversely divided and sub- 

 divided, and appearing to the eye a spongy cork-like mass, 

 coloured by the qualities of the air residing in the earth, with- 

 out which all roots die or remain dormant. Besides those 

 longitudinal layers, which form the structure of a root, and 

 which are so visible on the transverse section, there are other 

 woody rays which diverge from the exterior of the pith, and 

 terminate on the interior verge of the inner bark. 



The uses and office of the root are to fix the plant in the 

 soil, and to extract or receive therefrom the various qualities 

 necessary to the deyelopement of itself and the other parts of 

 the plant. The fibres, which have been already described, are 

 the agents which visibly receive those qualities, which are the 

 food of the plants; but a conjecture is admissible, whether the 

 tubercles on the bark be not also recipients of some quality or 

 other. Of the use of the fibres, however, there is no doubt : 

 we see them in full exertion while vegetation proceeds, and 

 languid or inert when growth is stationary. From every 

 observation which practical attention has been able to make, 

 whether from the stump of an amputated root, or from the end 

 of a cutting placed in favourable circumstances in the soil, 

 they appear to originate from the interior edge of the inner 

 bark ; and, in fact, are nothing else than elongations of the 

 extreme, or lower, ends of the fibres, which compose that 

 organ. When they issue from a layer, they may be traced to 

 the same part of the vegetable structure, not as originating 

 there, because this would be supposing an entity to proceed 

 from a nonentity, which is impossible : no ; their origin is the 

 vital lieart or corculum, whence they and all the organisation 



