PHENOMENA OF PLANT-LIFE. 93 



FIG. 16 shows the top of the squash, with the marks of the harness irons 

 upon it. 



FIG. 17 represents a piece of the root of an apple tree which penetrated 

 a bed of coarse, dry gravel, to the depth of more than eight 

 feet, and as it enlarged adapted itself to the spaces between 

 the pebbles, and in some cases entirely inclosed them. 



FIG. 18 illustrates the manner in which the roots of a black spruce grew 

 on Moose Mountain, in New Hampshire. The soil was only 

 a few inches deep, and below was solid rock, so that as the 

 horizontal roots increased in diameter, they lifted themselves 

 out of the ground, and of course raised the entire tree every 

 year. 



FIG. 19 shows how the heart of a yellow birch, growing on a ledge in 

 Hanover, N. H , has been carried upward and outward by the 

 annual deposition of wood, from the rock on which it must 

 have rested when the seed germinated The peculiar thick- 

 ening of the trunk and roots near the base is often seen in 

 trees on exposed situations. 



FIG. 20 is a section of the stem of a tree (Hibiscus splendens) about four 

 inches in circumference, from which all the bark and most of 

 the wood was removed. A portion of the outer layer of sap- 

 wood, one inch long and seven-sixteenths of an inch in circum- 

 ference, was left to convey the sap to the foliage, which had a 

 surface of twenty-five hundred square inches. Not a leaf 

 wilted, but the supply of water was abundant for the growing 

 tree 



FIG. 21 exhibits a section of a similar stem from a portion of which 

 the wood was entirely removed, while the greater part of 

 the thick, succulent bark remained. The foliage had a surface 

 of five hundred square inches, while the amount of living bark 

 which formed the connection between it and the roots was at 

 least five times as large as the piece of sap-wood in the pre- 

 ceding figure. The leaves wilted as quickly and completely 

 as if the stem had been entirely severed. 



FIG. 22 is a piece of wood from a red maple, which threw out a callous 

 from its ends like a grape cutting, and grew, although it had 

 neither roots nor buds. 



FIG. 23 shows a section of an elm root which was girdled, inclosed in a 

 glass tube so as to exclude the air, and then replanted in the 

 earth, its connection with the tree remaining intact A new 

 bark and layer of wood formed from the cambium which had 

 been previously deposited. 



FIG. 24 exhibits a section of the trunk of a small elm, upon the bark of 

 which a horizontal incision was made, and above this four 

 vertical incisions three inches long. The four quarters of the 

 bark were then turned up, and a piece of tinned copper, one 

 inch wide, was wrapped around the wood. The bark was 

 then replaced, covered with waxed cloth, and securely fas- 

 tened down. This was do-ne on the thirtieth- of May. 

 13 



