AND ITS DIFFERENT KINDS. 103 



suppose, as some have done, that the tree had any in- 

 formation of the store of food at the foundation of the 

 wall, and voluntarily sent down its root to obtain it ; nor 

 is it wonderful that the Author of life should provide 

 for it as effectually as it could for itself, had it really 

 been a reflecting being.(18) So in the case of the 

 grasses in question, I presume the herb being in the 

 first instance starved, by a failure of the nutrimental flu. 

 ids hitherto conveyed by the water of the soil, its growth 

 would be checked, and when checked, the same growth 

 could not, as we know by observation on vegetation in 

 general, be instantaneously renewed. A sudden fresh 

 supply of food would therefore cause an accumulation 



(18) [" A tree growing upon a wall and unconnected with 

 f.lie earth, will almost of necessity grow slowly ; and as it must 

 be scantily supplied with moisture during the summer, it will 

 rarely produce any other leaves than those which the buds con- 

 tained, which were formed in the preceding year. Some of the 

 roots of a tree thus circumstanced, will be less well supplied 

 with moisture than others, and these will be first affected 'by 

 drought : their points will in consequence become rigid and in- 

 expansible, and they will thence generally cease to elongate at 

 an early period in the summer. The descending current of sap 

 will then be employed in promoting the growth and eiongatioa 

 of those roots only which are more favourably situated, and 

 those, comparatively with other parts of the tree, will grow 

 rapidly. Gravitation will direct these roots perpendicularly 

 downward, and the tree v/ill appear to have adopted the wisest 

 and best plan of connecting itself with the ground ; and it will 

 really have employed the readiest means of doing so, as effec- 

 tually as it could have done if it had possessed all the feeling« 

 and instinctive passions and powers of animal life. The subsp- 



