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TEXTBOOK OF BOTANY 



Fig. 1 10. — A mangrove {Rhizophora 

 conjugata), showing the numerous prop 

 roots. After Kerner. 



which they in turn pro- 

 duce, a single tree may 

 extend over a great area. 

 Stories are told of a 

 banyan tree that shel- 

 tered Alexander's army 

 of 7,000 men, and of an- 

 other in whose shade was 

 built a village of a hun- 

 dred huts. 



198. Storage.— Thick- 

 ened roots that serve for 

 the storage of food are 

 likely to be useful to 

 man, and so it is that 

 many plants with storage 

 roots are cultivated. 

 Such plants are often 



biennials, like the carrot, beet, turnip, and 

 parsnip. The plant manufactures food 

 during the first year of its life and stores 

 it in the thick tap (primary) root. The 

 work of absorption from the soil is done 

 chiefly by short branch roots. It is not 

 merely the root that lives over winter ; 

 there is a short, thick stem attached to 

 the top of the root and not sharply marked 

 off from it. During the plant's first year, 

 this short stem bears a cluster of root 

 leaves ; the next year it grows into a tall 

 flower-stalk, and much of the food stored 

 in the root is used in forming flowers, seeds, 

 and fruits. 



But it is not only biennials that have 

 thick storage roots. Radishes, for ex- 



FiG. III. — Root 

 of the radish, a 

 typical storage root. 

 The stem is the very 

 short portion at the 

 upper end of the 

 large root, to which 

 the leaves are at- 

 tached. 



