98 AERIAL AND SUBTERRANEAN LEAF-BUDS. 



and another cluster of leaves,/and r, forming a young plant with roots; 



from this a third axis comes off, a'", and so on. In many instances 



the runner decays, and the 

 young plant assumes an inde- 

 pendent existence. Gardeners 



imitate this ** tlie Propaga- 

 tion of plants by the process 

 of layering, which consists in 

 bending a twig, fixing the 

 central part of it into the 

 ground, and, after the pro- 

 duction of adventitious roots, 

 cutting off its connection with 

 the parent. 



192. When the stem creeps along the surface of the ground, as in 

 the Rhizome (fig. 90), or completely under ground, as in the Soboles 

 or creeping stem (fig. 91), 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. 91 

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

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

 being the level of the ground. Again, in fig. 90 (rhizome of Solomon's 

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

 1) the bud which has sent up leaves, and which has decayed, c c being 

 the scars left by the similar buds of previous seasons. 



193. Aerial and Nnblerrniiean Lent-bud*. 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, sub- 

 terranean buds are annually produced, which appear above ground 

 as shoots or branches covered with scales at first (fig. 110 /), and 

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

 a young branch). These branches are herbaceous and perish an- 

 nually, 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 



Fig. 206.- -Flagellum, or Eunner of the Strawberry, a', One axis which has produced a cluster 

 of leaves, the upper, r, green, the lower, /, rudimentary. From the axil of one of the latter, a 

 second axis, a", arises, bearing about the middle a rudimentary leaf,/, and a cluster of leaves, 

 r, partly green, and partly rudimentary, at its extremity. From the axil of one of the leaves of 

 this cluster, a third axis, a'", proceeds. 



