DIVISION OF ROOTS. 19 



11. The extremities of the radicles are unprovided with epi- 

 dermis, and are composed only of rounded cellular tissue ; these 

 parts are called spongioles (little sponges), and, as we shall pre- 

 sently see, play a very important part in absorption. 



12. The general form of roots varies much, and gives rise to 

 numerous distinctions, the chief of which are the following : 



DIVISION OF ROOTS. 



Roots are primarily divided into Simple and Compound or Multiple 

 Roots. 



SIMPLE ROOTS have a single base continuous with the stem; they are 

 called 



Tap-roots, when they descend perpendicularly, and have almost the whole 

 of their spongioles united at their extremity. These are 



Fusiform, when they are shaped like carrots, and 



Napiform, Tuberous, &c., when they are swelled and rounded like turnips. 



Fibrous, when they are very branching and ordinarily furnished with 

 numerous spongioles. These are 



Knotted, when they present swellings along the course of their fibres, and 



Creeping, or Repent, when they run along near the surface of the soil. 



The second primary division of roots is 



The COMPOUND ROOTS : they arise in great numbers from the neck of the 

 plant. They are said to be 



Branching, or Capillary, when each fibre, which is distinct at its origin, 

 gives off branches in abundance ; 



Knotted, when the fibres have swellings or knots in their course ; and 



Fusiform, or Fasciculate, when they are formed by the union of a great 

 many more or less elongated tubercles. 



13. We may add that roots are said to be fleshy, when they 

 are more succulent (juicy) and larger than the base of the stem, 

 and ligneous, when their tissue resembles wood. They frequently 

 present swellings or tubers, which are always masses of nutritive 

 matter destined to supply the wants of the plant at a certain 

 period. 



14. Finally, we give the name of adventitious roots to those 

 which, in certain instances, arise from the stem, but are in other 

 respects analogous to ordinary roots. (See pages 63 and 64.) 



OF THE STEM (CAULIS). 



15. We give the name of STEM (Cavlis, Stalk) to that part 

 of plants which is intermediate between the roots and the leaves. 



11. What are spongioles ? 



12. What is a simple root? What is a tap-root? What is a fusirbrm 

 root? What is a napiform root? What is a fibrous root? What is a 

 knotted root ? When is a root said to be creeping ? What is a compound 

 root ? What is a capillary root ? 



13. What is meant by a fleshy root ? What is meant by a ligneous root? 

 What is the use of those swellings or tubers found on certain roots ? 



14. What are adventitious roots ? 



15. What do you mean by stem ? 



