76 EXPERIMENTS WITH PLANTS 



so placed that the strainer slips down easily between 

 them. Pieces of glass tubing about an inch long are 

 attached by sealing-wax to the sides of the strainer in 

 the manner shown in the figure. (This is most easily 

 done by attaching lumps of wax to the tubes, placing 

 them on the nails and then heating the strainer at the 

 proper points. On placing it in position the wax will 

 adhere to it.) They should be large enough to slip 

 easily over the upright guides. A hole large enough to 

 receive a small flower- pot is now bored in the board 

 and two upright side - pieces nailed on so as to prevent 

 the pot from resting its weight 'on the table. The 

 strainer should slide on the guides with a minimum 

 amount of friction. 



It must be remembered that if we prevent the stem 

 from bending (e. g., by enclosing it in plaster of 

 Paris), it will probably exert a much greater pressure. 

 Tne amount which is registered by any of these 

 methods is only a very rough approximation and is, 

 as a rule, much smaller than what the plant can exert. 



We must not be too hasty in thinking the limit of 

 weight has been reached; for, after waiting a week 

 or so, the plant will sometimes begin to lift a load 

 which seemed at first too heavy for it. 



Plants sometimes come up through soil which is 

 extremely hard. It is interesting to watch the be- 

 havior of the plants in a very hard, resistant soil. 

 Observe all the cases you can. Plant some Beans 



