ELEMENTS OF STRUCTrrAL IMTAXV. 65 



arajjle, will take root at every joint, if tJie stem be laid 

 upon the ground (Fig. 90). The runners of the 

 Strawberry take root at tlieir extremities : and nothing 

 is more familiar than tlmt cuttings from various plants 

 will make roots for themselves if put into proper soil, 

 and supplied with warmth and moisture. All such roots 

 are produced from some other part of the stem than the 

 radicle, and are called secondary or adventitious roots. 

 When such roots are developed from parts of the stem 

 which are not in contact with the ground, they are 

 aerial. 



87. There are a few curious plants whose roots never 

 reach the ground at all, and which depend altogether 

 upon the air for food. These are called epiphijtes 

 There are others whose roots penetrate the stems and 

 roots of other plants, and thus receive their nourish- 

 ment as it were at second-hand. These are parasitic 

 plants. The Dodder, Indian-Pipe, and Beech-di'ops, of 

 Canadian woods, are well-known examples. 



88. The Stem. As the root is developed from the 

 lower end of the radicle of the embryo, so the stem is 

 developed from the upper end, but with this important 

 difference, tliat a hud always precedes the formation of 

 the stem, or any part of it or its branches. Between 

 the cotyledons of the Bean (Fig. 71), at the top of the 

 radicle, we found a minute bud called the jilumule. Out 

 of this bud the first bit of stem is developed, and during 

 the subsequent growth of the plant, wherever a branch 

 is to be formed, or a main stem to be prolonged, there 

 a bud will invariably be found. The branch buds are 

 always in the axils of leaves, and so are called 

 arillanj. Adretititious buds, however, are sometimes 

 produced in plants liko thr Willow, particularly if the 



