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 wdth 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° — 17° 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 



