262 THE AMERICAN MONTHLY [Aug. 



base of the series and then note that the buds in line 

 over each other are in similar numerical series. Does dif- 

 ference in shape or size of specimens affect the law of 

 position of the buds ? Compare the potato with twigs 

 of shrubs or trees, and with convenient herbaceous 

 stems, and notice: that all have a definite law rul- 

 ing the location of the leaf or flower buds, the law 

 differs with different kinds, the buds are closer as 

 you approach the apex of the stem. The potato is 

 thus comparable with other stems; it is in fact a modi- 

 fied stem growing beneath the ground, and used in the 

 economy of the plant for the storage of starch. — The 

 definiteness of location of the parts of a living being is 

 in general called symmetry, a revicAV of animals and 

 plants will convince you that it is a very general law 

 and that only slight departures from symmetry are 

 commonly if ever met with. Draw views showing as 

 many as possible of these points. 



2. Tissues of the Potato. — Cut as thin a slice as 

 possible completely across the specimen in the level of 

 one of the buds, examine this carefully, using the hand 

 lens and recognize that it is composed of three different 

 kinds of material, tissues, viz. : — (1) the bark, a thin brown 

 outer layer commonly called the skin ; (2) a thin layer 

 everywhere parallel with the bark except at the level 

 of the bud, where it runs to the bud and enters it, the 

 fibro-vascular tissue ; and (3) the parenchyma, filling in 

 all of the remainder of the specimen. — Cross-sections of 

 herbaceous stems, e. g., that of the geranium, will show 

 the same layers, the parenchyma or pith is however re- 

 latively much less extensive. Draw a general view of 

 the section, 



3. Cells of the Potato. — Cut a thin section of a 

 small part of the potato, passing through all of the dif- 

 ferent tissues, the slice must be thin enough to see 



