88 THE AMERICAN MONTHLY [April, 



If now, having examined the surface of the potato and learned 

 that it has a base and apex, a thin skin and eyes, the relative posi- 

 tions of which are governed by a very definite and simple law, 

 we cut the potato into halves by a slice, passing through the base 

 and apex and through as many eyes as possible, we can learn 

 still more about it. It is quite watery, as shown by the fluid 

 which collects upon the surface cut by the knife. With a dry 

 cloth, dry the surface. It will then present a granular appear- 

 ance of the well-known whitish color, and a uniform texture 

 throughout, up to the very narrow edge of the skin. A closer 

 examination will, however, show a wavy line, imperfectly par- 

 allel with the skin,, but perhaps an eighth of an inch below it; 

 the line is seen to come to the surface at the eyes, but to be as de- 

 scribed in all other locations. A cross section of the potato 

 through one eye will present the same circular ring of substance 

 parallel with the surface, except at the eyes. 



The rough study of the potato can easily be made to yield a few 

 more facts which we must take into account before we attempt to 

 interpret the potato in biologic language. If we place a potato in 

 moist and warm sand, sand which we have first carefully exam- 

 ined and proven to contain absolutely no organic matter of any 

 kind, and keep it warm for a few days, we shall see that the eyes 

 are the evident seats of activity, for they begin to enlarge. Later, 

 a stem bearing leaves emerges from each eye, and these leaves 

 are the precursors of subsequent ones on a further elongation of 

 the same stem. The stems thus elongate all in the direction of 

 the apex of the potato. If it was planted apex upward, they rise 

 above the sand and the leaves become green. A removal and 

 examination of the potato shows that the growth has been at- 

 tended with decay of the substance of the potato, which we may 

 safely infer, since the sand contains no organic substance, has 

 gone into the construction of the growing stems and leaves. 



The facts now acquire significance ; the eyes are buds, the potato 

 then a bud-bearing portion of the plant or a stem (an imderground 

 stem), and one considerably modified in shape; it is connected 

 below with the plant and bears a terminal bud at its tip, and the 

 eyes are lateral buds, the skin is dark, and the circular layer par- 

 allel with it is comparable with the woody zone of ordinary stems, 

 while the bulk of the potato is thus a pith. If we were to imagine 

 a stem, as of elder, vastl}- distended by growth of pith at its tip, 

 nearly destitute of wood because living underground where it did 

 not require support, we should have such a growth as that of the 

 potato. If the potato be such a modified stem, its cell-structure 

 and life ought to help to make the case still more clear. Studies 

 bearing on this will follow in a succeeding chapter. 

 (To be continued.) 



