48 



LIVING PLANTS 



Power 



of movement 



Qiaracteristics 

 of mimosa 



tiplied and includes among other families the 

 Euphorbiaceas and Marantaceae. The groups 

 mentioned have shown a peculiar fitness for 

 tropical environment. One genus alone, 

 Cassia, includes four hundred and fifty species, 

 nearly all of which are at home in countries 

 near the equator. One of the northern repre- 

 sentatives, Cassia chamaecrista, has acquired 

 the name of the ''Wild Sensitive Plant" 

 throughout the middle and northern states, 

 while Cassia nictitans is similarly designated 

 in New England. Southward the number of 

 species increases with that of the other legum- 

 inous plants until near the equator, represen- 

 tatives of the group form a very large propor- 

 tion of the total mass of vegetation. 



Mimosa padica the "Sensitive Plant" or 

 "Shameweed" of the West Indies is one of 

 the most attractive members of this group, 

 since in addition to the typical adjustments of 

 the leaves, which it performs with great ra- 

 pidity and delicacy, it also exhibits reactions 

 to other and unusual stimuli. The move- 

 ments of plants are generally so slowly made 

 as to be incapable of detection except by re- 

 peated or long continued observation. Mi- 

 mosa, however, is one of the small number 

 which is capable of rapid movement of large 

 organs. This fact, and the great degree of ir- 

 ritability shown, drew the attention of the 



