12 BOTANY 



show that the root-like organ is really a stem. In 

 their internal anatomy the two organs differ essentially, 

 as we shall see in the next chapter, and there are cases 

 of modified leaves and stems which have departed so 

 far from the normal that the external morphology 

 gives no clue to their real nature, and then the anatomy 

 alone can determine to which category each belongs. 



The typical root is a colourless or brown series of 

 circular or flattened branches. It is never broad and 

 expanded like leaves, though in some cases, e.g., epi- 

 phytic orchids, it may be green. The main root is the 

 continuation of the original primary root of the seedling, 

 which has subdivided indefinitely with its growth, and 

 this is often supplemented by further roots which arise 

 adventitiously on the stem wherever they are needed, 

 either in the soil, in the air, or in water. A sprig of 

 Mint or Ivy left in a jar of water will often show the 

 white tufts of adventitious roots springing out of the 

 base of the stem. The great prop roots of the Mangroves 

 and some of the tropical species of Ficus are woody 

 and covered with bark, so that it is hard to find any 

 external feature other than their position by which 

 to distinguish them from the stem-trunks. 



The Stems which support the leaves and connect 

 them with those sources of food supply, the roots, are 

 generally upright, cylindrical, and branched in the air. 

 They have, however, an infinite variety of form, and 

 range from the sturdy Oak to the slender climbing 

 Convolvulus, from the great pudding-like Cactus and 

 swollen masses of the Potato to the slender threads of 

 the water Ranunculus ; and from the root-like Solomon's 

 seal running underground, to the contracted stem of 

 the serial Orchid perched aloft on the branches of other 

 plants, so that it never comes down to earth. Normal, 



