On the Roots differmg in each Soil. 323 



nrtica mens, cdyssum, and many others it .would be tedious to 

 mention, but which take ahnost all their nourishment from the 

 atmosphere*; see Plate VII. fig. 4. 



Rock plants being of a perfectly different form, have no radl- 

 cilia ; they have instead a little sort of instrument which licks up 

 tl^.e water from the stones, to keep the stem moist enough to al- 

 low the seeds formed in the root to rise through it to the buds. 

 The trilling degree of earth found in most rocks appears to give 

 sufficient litjuid to form the seeds, and this is all that is required 

 from the root of a rock vegetable ; for all the nutriinent is given 

 either by the leaves if they have any, or the stems and flowers of 

 these plants ; every part is indeed open to the atmosphere. But' 

 when we turn from the vegeta!)le, which", like the rock plant, 

 takes all its nourishment from above, and observe those which 

 by degrees receive more and more of tlicir support from the 

 root, we areinunediately struck with the diifercnce not only in 

 form but iji appendages. Tiie clavey plant receives a pretty 

 e(|ual quantity of imtriment from the leaves and root. It has 

 almost always a stunted prcemovie or bitten-off root ; see fig. 7. 

 The side roots reach but a very little v.-av, thai they may not be. 

 cut off by the large lumps of clay that coagulate, and inclose 

 the moisture surrounding each vcgetalde. " But their short side 

 roots are loaded with radicula, which plainly show how much 

 more nutriment they must take from the earth than either sand 

 or rock plants: sometimes they have occasional hairs, but never 

 anv fibres. 



The chalk plant takes nearly two-thirds from the root, the 

 re^t from the atmosphere, i'liey have no very distinguished 

 sha])ed root, that part being sometimes large and thick, as in 

 Japnnaria officinalis audJlitoniaia acantlia; sometimes running, 

 as in the Antirrhinum repens: they have alwavs pretty nefuly 

 the same quantity of radicles, many more than the clayey plant?, 

 but no fibres, and rarely any hairs. Most of the clialk plants 

 have rather a thick cuticle to their root, but not so tliick as that 

 which always covers the clavey plant, for that is almost always 

 double: both are intended, I suppose, to guard the root from the 

 entrance of that putrid water but too apt to lodge within the 

 interstices of the clayey lumps. I conjecture this, because, the 

 defence (though still evicting) is not so great in the chalk as iu 

 the clay, neither is the first so troubled with the defect, bee 

 fig. 8, Chalk root.' 



* I much regret space is not allowed me to give many specimens in 

 driiwjn;^ of the roots, as they would btiikc tlic eye with the astoiiibliin^ 

 dilTereiice existing in t/iat part as appertuiiiiii;^ to each dillbrcnt soil. Biic 

 bliould 1 ever be aijlc to give this work to the ijublic properly, it will be 

 there cximplificd. 



X 2 As 



