114 AEEIAL AND SUBTERRANEAN LBAE-BUDS. 



or creeping stem (fig. 108), the terminal bud continues to elongate 

 year after year, thus making additions to the axis in a horizontal 

 manner. At the same time buds are annually produced on one side 

 ■which send shoots upwards and roots downwards. Thus, in fig. 108 

 (soboles of a Rush), r is the extremity of the axis or terminal bud, / e 

 the leaves in the form of scales, f a the aerial shoots or branches, 1 1 

 being the level of the ground. Again, in fig. 107 (rhizome of Solomon's 

 seal), a is the terminal bud which has been formed subsequently to b, 

 'b the bud which has sent up leaves, and which has decayed, c c being 

 the scars left by the similar buds of previous seasons. 



Abeial and Subteeranean Leaf-buds. — According to the 

 nature of the stems, leaf-buds are either aerial or subterranean; the 

 former occurring in plants which have the stems above ground, the 

 latter in those in which the stems are covered. In the case of 

 Asparagus and other plants which have a perennial stem below ground, 

 subterranean buds are annually produced, which appear above ground 

 as shoots or branches covered with scales at first (fig. 129 I), and 

 ultimately with true leaves. The young shoot is called a Turio (turio, 

 a, young branch). These branches are herbaceous and perish annually, 

 while the true stem remains below ground ready to send up fresh 

 shoots next season. In Bananas and Plantains, the apparent aerial 

 stem is a shoot or leaf-bud sent up by an underground stem, and 

 perishes after ripening fruit. In some plants several branches are sent 

 up at once from the underground stem, in consequence of a rapid 

 development of lateral as well as terminal buds ; and in such cases the 

 lateral ones may be separated as distinct plants in the form of suckers 

 (surculi). The potato is a thicliened stem or branch capable of 

 developing leaf-buds, which in their turn form aerial and subterranean 

 branches, the former of which decay annually, whUe the latter remain 

 as tubers to propagate the plant. Thus, in fig. 109, s s is the surface 

 of the soil, ^ a is the aerial portion of the potato covered vrith leaves, 

 t is the subterranean stem or tuber covered with small scales or pro- 

 jections, as represented at t b, from the axil of which leaf-buds are 

 produced. This provision for a symmetrical development of axillary 

 leaf-buds at once distinguishes the tuber of the potato from fleshy 

 roots, like those of the Dahlia. 



Bulb. — ^A good example of a subterranean bud occurs in the Bulb, 

 as seen in the Hyacinth, Lily, and Onion. This is, a subterranean 

 leaf-bud covered with scales, arising from a shortened axis. From the 

 centre of the bulb a shoot or herbaceous axis is produced which dies 

 down. New bulbs, or cloves, as they are called, are produced in the 

 axil of the scales arising from the subterranean axis. At the base of 

 the scales there is a flattened disc, varying in thickness, which is 

 formed by the base of the buds, and which has sometimes been called 

 the stem. The parts of the bulb are seen in fig. 224, where p marks the 



