CH. VIIl] MIMOSA. 203 



stimulation begin in the leaves nearest the watch-glass : 

 the bell should be then removed, as the plant is easily 

 injured by ammonia. 



(233) Mimosa; temperature. 



On the bottom of a glass cylinder place a layer of wet 

 sawdust in which a small Mimosa growing in a pot may 

 be sunk ; the cylinder is to be placed in a large inverted 

 bell-jar filled with water of which the temperature can be 

 varied by ice or by hot water as the case may be. The 

 cylinder must be covered with a glass plate through 

 a hole in which it is possible to touch the plant 

 so as to test its sensitiveness. To get a clear result the 

 temperature should be lowered from 20 C., at which the 

 plant is thoroughly irritable, to 11 or 12 C., although the 

 lower limit of irritability is about 15. Cooling the air to 

 this amount, by the addition of ice to the water in the 

 bell-jar, is a tedious process, and it would probably be 

 better to have a second bell-jar ready filled with iced 

 water, to which the cylinder containing the plant might 

 be transferred. 



(234) Mimosa : effect of darkness. 



If Mimosa is kept in the dark for several days it loses 

 its sensitiveness. The plant should be kept in a damp 

 atmosphere in a greenhouse at a temperature of at least 

 16 1*7 C. The best plan is to place the flower-pot in 

 a tray of wet sawdust and to invert over it a tin cylinder, 

 the rim of which should sink into the sawdust. We find 

 that 4 or 5 days are needed to destroy sensitiveness. In 



