LESSON 6.] SUBTERRANEAN FORMS I TUBERS. 



43 



Trillium or Birthroot (Fig. 67) life is reduced to a very narrow 

 span, only an inch or less intervening between death beneath and 

 young life in the strong bud annually renewed at the summit. 



103. A Tuber is a thickened portion of a rootstock. When slender 

 subterranean branches, like those of the Quick-grass or Mint (Fig. 

 64), become enlarged at the growing end by the accumulation there 

 of an abundance of solid nourishing matter, tubers are produced, like 

 those of the Nut-grass of the Southern States (which accordingly be- 

 comes a greater pest even than the Quick-grass), and of the Jerusalem 

 Artichoke, and the Potato. The whole formation may be seen at a 

 glance in Figure 68, which represents the subterranean growth of a 

 Potato-plant, and shows the tubers in all their stages, from shoots 

 just beginning to enlarge at the tip, up to fully-formed potatoes. 

 And Fig. 69, one of the forming tubers moderately magnified, 

 plainly shows the leaves of this thickening shoot, in the form of little 

 scales. It is under these scales that the eyes appear (Fig. 70) : 

 and these are evidently axillary buds (43). 



104. Let us glance for a moment at the economy or mode of life 

 of the Potato-plant, and similar vegetables, as shown in the mor- 



FIG, 68. Forming tubers of the Potato. 69. One of the very young potatoes, moderately 

 magnified. 70. Slice of a portion through an eye, more magnified. 



