108 THE AMERICAN MONTHLY [May, 



ally around the nucleus, as shown in figure 8, a, camera-lucida 

 drawing. The starch grains in later stages of the process become 

 so numerous as to prevent vision of their relation to the pro- 

 toplasm, but in deeper cells they can be seen in greater numbers, 

 till finally they entirely fill the cell, apparently to the entire exclu- 

 sion of the protoplasm. 



There would seem to be no limit to the extent to which this 

 secretion and deposit of starch and the growth and enlargement 

 of the tubes can extend, but the growth is merely an indefinite 

 continuation of the process just described. 



The only remaining tissues of the potato are those of the fibro- 

 vascular bundle, which is to be regarded as an aborted structure. 

 Two kinds of cells are characteristic of the zone, parallel with the 

 surface ; the long cylindrical cells of figure 9 and the spiral cells, 

 the side and one termination of which are shown in the figure. 

 The function of support of the spiral cell is not its function here, 

 for no support is required of a body in this position. If the yel- 

 low tinge in the epidermis be a dubious case of persistence through 

 inheritance of a now not used character, the fibro-vascular tissue 

 can be regarded, beyond question, as a vestigiary structure, point- 

 ing to a time when the stem was an aeriel organ in which the fibro- 

 vascular tissue was needed for support ; a case like the useless 

 eyes of moles and the coalesced neck-vertebrte of cetaceous and a 

 host of other inherited structures which imply ancestors in whom 

 these organs were functional. 



The buds are closer together at the apex of the stem and the 

 embyronic tissue of each is portioned out to it in the terminal bud, 

 which to the naked eye has others about it too close to be distin- 

 guished, and by the microscope is found to be making provision 

 for still other ones. To each one of these is imparted a small 

 portion of embryonic tissue, but this tissue is alike in all the buds. 

 As some perhaps look upon the potato, it appears to be a very 

 admirable source of food for man, but it is hardly biological to 

 attribute to the plant such exalted altruistic motives of disinter- 

 ested generosity as it might imply if we should intimate that this 

 is the end and aim of its existence. There is a class of mankind 

 who appear to deem it proper, like Pope, to hold all nature to ac- 

 count for itself as useful to man, and such would doubtless say 

 that the potato was created to be a food product. To the biolo- 

 gist's ways of thinking, this end of the potato's life is merely in- 

 cidental. From its standpoint a very unhappy incident ; the real 

 end and aim of the potato's life is to propagate its kind, the 

 storage of starch being a part of the plan. 



The life of the tuber of the potato is part of the larger life 

 of the entire plant. The history of the tuber is as follows : It 

 starts from a bud on a preceding '•^seed-potato," of which 

 and of whose predecessors it may be thought to form a part, 

 but really it is (like cuttings or slips from any plant) the begin- 

 ning of what we may call a new plant. The early growth of the 



