ROOTS FROM SHOOTS 125 



Moreover, if the tip be eaten by animals or otherwise 

 damaged, branches soon arise and these can be easily 

 seen to come out from the inside by narrow cracks, 

 and not from the surface as, we have learnt, do the 

 branches of the shoot. 



. That they ultimately come to look so like stems, 

 is due to the fact that though quite different in struc- 

 ture when very young, roots increase in thickness, 

 exactly as do stems, and form cork and bark in the 

 same way. These adventitious roots of the Banyan 

 serve of course to support the branches, and so enable 

 one tree to grow enormously and cover a great space- 

 of* ground. There is one very famous tree in Cal- 

 cutta whose stem-Hke supports number about 500, 

 and bear a crown of branches of over 900 feet in 

 circumference, and other trees famous for their size 

 are found in Madura and other places. The adven- 

 titious roots of cereals and palms, also act as extra 

 holdfasts and supports to keep the stem upright. Such 

 supporting roots are better developed in the Screw- 

 pine, PANDANUS, where they are sometimes a couple of 

 inches thick, and have very large scaley root-caps (fig. 2). 

 Several trees which habitually live in the mud- 

 flats of tropical seashores, also have adventitious 

 supporting roots which, like those of Pandanus, grow 

 down obliquely into the mud and form a much better 

 and firmer support for the plant than a single thick 

 stem, which might be washed away by a strong tide, 

 could do. These trees are called MANGROVES, and 

 they grow very commonly in the tropics by the mouths 

 of rivers and wherever the seashore is soft and 

 muddy. 



