Stone : The power of growth of ostrich ferns 225 



about 1 8 tons, which is annually being Hfted higher and higher 

 by the root situated between the two halves. 



The experiments made some years ago by Clark, at the Massa- 

 chusetts Agricultural College, in harnessing a squash, showed that 

 it was capable of growing and developing under a weight of 5,000 

 pounds, but from data obtained in this experiment it would appear 

 that there were not more than two or three atmospheres developed 

 in the cells, and hence not remarkable from the point of view of 

 pressure exerted by the cells. The average pressure exerted by 

 ordinary growing cells is from one to three atmospheres, but by 

 resorting to stimulation this pressure may be enormously increased 

 and may even exceed one hundred atmospheres, as in the case of 

 moulds growing in concentrated solutions. 



