58 THE STEM. [CHAP. 



I may be found apparently contradicting Nature. In 

 such cases do not rest satisfied with reference to a single 

 specimen : compare together a number of specimens 

 whenever it can be done, and you will then find, I 

 believe, the illustration confirmed. In explaining the 

 terms used to denote the mere outline and form of 

 organs, I have not generally referred to any species in 

 illustration. I leave them to the learner to find out for 

 himself. 



2. THE ROOT. In the germinating Bean we find that 

 the root is developed by the direct downward elongation 

 of the radicle of the embryo. A root thus originating 

 when it persists, forms what is termed a tap-root. We 

 have good examples of this primary root-axis in a large 

 number of Dicotyledons, both trees and herbaceous plants, 

 though in many, by arrest or by repeated branching, it 

 loses, more or less, its character as a proper tap-root. 

 In the Carrot and Beet, the tap-root thickening very 

 much becomes fusiform in shape, and usually remains 

 undivided, giving off delicate fibrils, which play an 

 important part in the work of absorption. In many 

 Monocotyledons, owing to the origin of the root from 

 root-buds which burst through the undeveloped or early 

 arrested radicle of the embryo, we never have a tap-root. 

 In these plants the root generally consists of numerous 

 independent fibres, branched or unbranched. It may be 

 described simply as fibrous. Pull up any grass, and you 

 will find such a root. 



In our first lesson we referred to a kind of Buttercup 

 which forms creeping stems, giving off root-fibres at the 

 nodes. This is a very frequent condition, and many her- 

 baceous plants, both Dicotyledons and Monocotyledons, 

 are principally multiplied, and the area which they occupy 

 extended, by such creeping, root-producing stems. Roots 

 originating in this way, and not by direct prolongation of 

 the radicle of the embryo, are distinguished as adventi- 

 tious. When adventitious roots are given off by climbing 

 or erect stems, as in the Ivy and very many trees growing 

 in hot, moist climates, they are termed aerial. 



Keeping the distinction between true and adventitious 

 roots in view, it will be clear, from what we have said of 

 the origin of the root-fibres in certain Monocotyledons, 



