ENDOGKNS. 



plete development of the root, stem, and leaves tliau 

 in the other types, giving a character to the external 

 form of plants which enables us to recognize them 

 and place them in a natural system of classification. 

 It is therefore appropriate here to consider these 

 structures in as brief and comprehensive manner as 

 possible. 



4. If a pea or bean be soaked in water, and the 

 leathery skin be stripped off, two large fleshy masses 

 will be seen (the cotyledons) inclosing a small cylin- 

 drical body, (the axis^ which bears two minute leaves 

 at its extremity. The cotyledons and axis together 

 constitute the embryo. 

 In the growing plant 

 the stem grows from 

 the axis upward and 

 the root downward, 

 and the leaves develop 

 only on the ascending 

 part of the axis and not 

 on the root. 



In the growing stem 

 the terminal cells (a, 



' Fig. 26, A) multiply 

 and enlarge. They fur- 

 nish new cells to the 

 cambium layer, or that 

 between the bark and 



Fig. 26. 



