PHENOMENA OF PLANT-LIFE. 23 



its growth. While it has been demonstrated by Prof. Asa Gray 

 that two points in a vertical line on the trunk of a tree will not 

 separate as it enlarges, it seems equally clear that both of 

 them may be quite perceptibly elevated in the course of time. 



It has been stated on good authority that, at Walton Hall, 

 in England, a mill-stone was to be seen, in 1863, in the cen- 

 tre of which was growing a filbert tree, which had completely 

 filled the hole in the stone, and actually raised it from the 

 ground. The tree was said to have been produced from a nut, 

 which was known to have germinated in 1812. The above 

 story has been declared false, because, as asserted, the tree 

 could not have exerted any lifting power upon the stone. It 

 is, however /not difficult to see that it may be true, and is even 

 probable. 



Yet it should be remembered that the amount of elevation, 

 in any case where it occurs from the increase in the size of 

 horizontal roots, must depend upon the firmness of the mate- 

 rial on which they rest, and can never exceed one-half the 

 diameter of the largest roots. When, therefore, a writer, as 

 has happened, asserts that, during a visit to Washington Irv- 

 ing at Sunny side, he carved his name upon the bark of a tree 

 beneath which he was sitting in conversation with the illustri- 

 ous author, and that many years after he went to the place, 

 and with much difficulty discovered the identical inscription, 

 high up among the branches, far above his reach, it is alto- 

 gether probable that his feelings were too many and too ex- 

 alted for the ordinary use of his intellectual faculties. 



Since the publication of the paper on the " Circulation of 

 the Sap in Plants." in the last volume of the Agriculture of 

 Massachusetts, a course of lectures on the "Physiology of 

 the Circulation in Plants, in the Lower Animals, and in Man," 

 by Dr. J. Bell Pettigrew, has been published by Macmillan & 

 Co., of London. The hypotheses adopted by this author are 

 quite extraordinary, and .evidently announced without the 

 slightest attempt at demonstration, although he has invented 

 a new method of accounting for the phenomena of the motions 

 of the sap. Thus he says, "In trees the sap flows steadily 

 upward in spring, and steadily downward in autumn." Also, 

 "Much more sap is taken up than is given off in spring, in 

 order to administer to the growth of the plant. In autumn, 



