38 ON" STEMS. 



ihe lower you descend, the more you find the branches 

 increase in size and diminish in number, till at length 

 you reach the original and single stem. 



Caroline. But what is the difference between a sub- 

 terraneous stem and a root ? 



Mrs. B. The structure of the root and of the stem 

 is in some respects different, Eftid their functions totally 

 so : the former merely sucks up nourishment from the 

 soil and transmits it to the leaves ; the latter is supplied 

 with organs to distribute it, variously modified, to the 

 several parts of the plant, the leaves, the flowers, &/c. 



There is a point or spot separating the stem from the 

 root, called the neck, which may be considered as the 

 seat of vitality. If you cut off the root of a young plant, 

 it will shoot out afresh ; if you cut away the stem, it will 

 be renovated ; but if you injure this vital spot, the plant 

 will infallibly perish. 



Emily. I think it should be called the heart rather 

 than the neck of the plant, since it is so essential to its 

 existence. 



Caroline. Is not the neck equally so ? Animals will 

 not survive decapitation any more than plants. But it is 

 true the situation of the neck does not quite correspond 

 with that of the animal frame, unless you denominate the 

 roots the body of the plant, and the whole that is above 

 ground the head. 



Mrs. B. I do not think the huge trunk of a venera- 

 ble oak would yield that title to its roots, and the extrem- 

 ity of its branches crowned with verdure would lay exclu- 

 sive claim to the dignity of head. 



The stems of plants are divided into two classes : 

 those which grow internally, and those which grow ex- 

 ternally. M. De Candolle distinguishes them by the char- 

 acteristic appellations of endogenous and exogenous, a dis- 

 tinction first introduced by a celebrated French botan- 

 ist, M. Desfontanes. We have no corresponding terms 



163. What is the difference between a subterraneous stem and a root? 

 164. Where is the seat of vitality in plants? 165. What will be 

 the consequence if the root of a young plant is cut off; or if the stem be 

 removed; or if the vital part be injured? 166. To illustrate the 

 subject, what comparison is made between plants and the animal frame? 

 167. Into what two classes are the stems of plants divided? 168. 

 Hew are they designated by De Candolle? 



