222 BOARD OF AGRICULTURE. 



At 4, p. m., Aug. 28, it was 29.47 feet, Temp. 75° Fahr. 



[For illustrations relating to the squash, see figures 1-1G.] 



Gauges were also attached to the stumps of large plants of 

 Indian corn, tobacco, and the dahlia. The results were not 

 specially different from what has been previously observed by 

 Hofmeister and others. The flow continued but a very few 

 days, and the pressure varied from eight to twenty-five feet 

 of water. The pressure in all these cases seems to bo caused 

 by the activity of the absorbent tissues of the root ; and its 

 cessation results, doubtless, from the stagnation of the sap in 

 the gorged cells and vessels, and the consequent decay of the 

 root-hairs and fibres. 



The frequent displacement of flagging-stones, and the dam- 

 age often done to brick and concrete pavements and stone 

 walls by the roots of shade trees, considered in connection 

 with the wonderful expansive power exhibited by the squash 

 in harness, made it. evident that growing roots of firm wood 

 must be capable of exerting, under suitable conditions, a 

 tremendous mechanical force. Upon searching the fields for 

 examples of trees standing upon naked rocks, or ridges 

 covered with only a shallow soil, many interesting specimens 

 were readily discovered to demonstrate this fact. 



In South Hadley, Mass., a sugar maple was found which 

 had gri wn upon a horizontal bed of red sandstone. The tree 

 stood upon the naked rock, over which its roots extended a 

 few feet in three directions into the soil. One root had 

 pushed its way under a slab of rock which measured more 

 than twenty-four cubic feet, and must have weighed about 

 two tons. In the course of twenty years or more, this root 

 had developed to such a size as to raise the slab entirely from 

 the bed-rock and from the earth, and so that it rested wholly 



