SEED AND ROOT 



181 



FIG. 225. VEGETABLE COAST-GUARDS. 



Lyme-grass, Sea-sedge, Marram-grass, and Sea-holly are most useful plants on sandy shores, as their roots and under- 

 ground stems hold the loose sand together, and prevent it being washed away by the sea or driven inland by the wind. 



See also fig. 237. 



feelings, and to shriek when torn from the earth ! It was, therefore, 

 accounted dangerous to disturb them. 



Fibrous roots are seen in the Grasses, Buttercup (Ranunculus, fig. 223), etc., 

 the name being given to branch-roots which are very slender. The fibres 

 sometimes penetrate to a greater depth than people are inclined to suppose, 

 particularly when the subsoil is hard and dry, and the plants are needing 

 more abundant nourishment. Even in rich garden soil the roots of Wheat 

 (Triticum) have been traced to a perpendicular depth of five or six feet. 

 This, however, is nothing in comparison with the depth to which some tap- 

 roots will penetrate. One hundred and ten feet is the computed length of 

 the tap-root of a Baobab-tree (Adansonia digitata) in Adanson's account of 

 Senegal ; but this, we need scarcely add, is exceptional. 



In the fibrous roots of many plants we find peculiar swellings and thicken- 

 ings, which serve (like the different forms of tap-root) as reservoirs of 

 nutritious matter ; and these may all be described as tuberous roots (fig. 226). 

 Care must be taken, however, not to confound a tuberous root with a tuber, which 

 last is not a root at all, but a fleshy underground stem (cf. Chapter VII.). 

 In Pelargonium triste the tubercles or swellings give the fibres a beaded 



