34 EASY LESSONS IN VEGETABLE BIOLOGY. 



are made by the union of cells into groups. Obser- 

 vation has shown that in the higher plants new 

 cells are not produced every-where uniformly, but in 

 particular spots. To places of this kind the terms 

 growing-point and growing r , or formative, layer have 

 been applied. Growing-points may be seen in the 

 tips of buds, and formative layers between the wood 

 and bark of trees. The names formative or generat- 

 ing tissue have been given to the tissue which is here 

 formed by the division and union of cells. A tissue 

 in which the cells are not capable of self -division is 

 called a permanent tissue. 



3. In direct contrast to the generating tissues are the 

 healing tissues, or cork tissues. In these the cells 

 lose their cell-sap, and the cellulose of the walls be- 

 comes converted into cork, which is of great im- 

 portance as the true healing tissue of plants. This is 

 formed like a cushion, or callus, over the surface of 

 a wound in a tree. The cuttings of the cochineal 

 cactus would decay at once if set in the ground with 

 the surface of the wounds fresh. They are therefore 

 laid for some time in the sun, in order that a cork 

 tissue may be formed, which closes the wound and 

 prevents decay. Such facts not only prove that the 

 living vegetable is governed by other than invariable 

 mechanical forces, but are also mute prophecies of 

 higher truths revealed to the human intelligence in 

 God's word relative to the healing of the soul. 



