184 DICOTYLEDONS LABIATE DIAGRAM 12. 



is made into small lumps like pieces of chalk, which are exported 

 into all parts of the world. The indigo is one of the best dyes for 

 its fastness, and one of those which are most easily renewed. 

 The Sensitive Plant is a small leguminous plant which only 



grows in hot coun- 

 tries, but is often 

 grown in green- 

 houses because of 

 the curious sensi- 

 bility to which it 

 owes its name. In 

 the evening, its com- 

 pound leaves close up 

 Leaf of Sensitive Plant, open. The same closed. and hang down to 



sleep ; and those of nearly all leguminosse act in the same manner. 

 We have already spoken of the sleep of the clover, and of the false 

 acacia. What is peculiar in the sensitive plant is, that when the 

 leaves are expanded and the weather is warm, they close and droop 

 immediately if touched, as if they were going to sleep. Little 

 by little they rise up and re-open slowly, to close and droop 

 again, as soon as they are touched anew. 



FAMILY LABIATE, 

 [ DIAGRAM 12. ] 



The Labiatce, like the Leguminosse, form a family in which there 

 is a very considerable resemblance between the plants. We may 

 take the white dead nettle as an example, though it is not a useful 

 plant to man. We notice immediately that the stalk is square, 

 unlike that of most plants ; moreover the leaves are always 

 arranged two and two on the stem ; they are opposed, as it is said 

 in similar cases. The calyx is formed of a single piece in five 



