112 APPENDIX. 



herbaceous plants have not any pith, and that I 

 have seen the trunks of large trees destitute of it, 

 and they have yet continued to grow and to bear 

 fruit ; so that the order of vegetation may be ex- 

 plained without it; and indeed was I here to take 

 notice of the several particulars in plants, I might 

 swell this treatise into a large volume. . . . 



"The motion of the sap continues in a plant so 

 long as the sun's warmth can keep it in a fluid 

 state ; but it is condensed or thickened by a win- 

 ter's cold, and is thereby changed into the con- 

 sistency of gum, and being thus stagnated, cannot 

 move any more till the w^armth of the following 

 spring or some artificial heat rarifies it into its 

 former liquid state. It then renews its former 

 vigour, and pushes forth branches, leaves, etc. 

 But we must not suppose it is only the melted sap 

 that was thickened in the tree during the winter 

 which does that office of germination. The root 

 has not been idle while the branches have stood 

 still ; it has not lost the moisture of the preceding 

 autumn to impregnate and furnish itself with 

 proper salts or nouriture, from whence the tree is 

 to be maintained. Here is a supply laid in to 



