BOOTS. 17 



7. In case of many plants, the so-called annuals, the roots 

 and other parts live but one season. The roots of biennials, 

 such as the Carrot, Teasel, etc. live through two seasons. Per- 

 ennial roots continue to live from year to year, though the 

 stem in some cases dies down at the end of each season. Sec- 

 ondary roots may arise from different parts of the plant — 

 stems and branches — whether above or below the ground. 

 Such are called adventitious roots. They are common in 

 creeping plants, especially at the joints, and their production 

 is usually favored by contact with moist soil. In the Trumpet 

 Creeper, Poison Iv}^, etc., they assist the plant in climbing, and 

 since they do not grow into the ground they are called aerial 

 roots. In some rare cases the aerial root is a tendril, as in 

 Vanilla aromatica. In some species of Jussisea (swamp plants) 

 some of the adventitious roots develop into floats. 



8. Aerial roots are more common in moist tropical coun- 

 tries, especially in deep forests where the light is partially ex- 

 cluded — it being unfavorable to their development. A notable 

 example is furnished by the Banyan-tree of India, and some 

 other Fig-trees. Their outstretched branches send down adven- 

 titious roots, that grow into the soil and thus become support- 

 ing columns. The Screw-pine is sometimes lifted up by roots 

 that are exposed some distance from the ground. The Sugar- 

 cane produces aerial roots from many joints similar to those 

 near the base of Indian Corn. The seeds of the Mangrove of 

 the West Indies sprout before falling from the tree, and send 

 a long root down into the mud, in which these trees grow, 

 thus gaining a foothold before severing their connection with 

 the parent tree. 



9. Aerial roots, whose function is somewhat different from 

 the above, are found in Air-plants, or epiphytes (Gr. epi, upon ; 

 phyton, plant). They generally grow on other plants, as their 

 name signifies, but their roots serve merely to give the plant 

 attachment, and the food is derived wholly from the air. 

 Many of the beautiful Orchids of the tropics are of this na- 

 ture. The Epidendron, or Tree Orchis (growing on a species 

 of Magnolia), and the Tillandsia, or Spanish Moss (hanging in 



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