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THE AMERICAN BOTANIST. 



the surface like those of our common potato. Like that spe- 

 cies, too, the tip is the part reserved for storage and is rounded 

 out into a shape approaching spherical. It produces no roots 

 and the stem along which the food is brought for storage is 

 slender and apparently intended merely to transport the food. 

 The tuber still bears scales that are manifestly homologous 

 with the leaves on the aerial stems and they subtend the buds 

 that will give rise to new aerial stems next year. These leaf- 

 like parts are not so clearly discerned on the potato, which is 

 the tuber par excellence, but they may be found forming part 

 of the "eyes," as the transformed nodes of the stem are called. 

 The sunflower tubers lack the corky outer layers of cells that 

 keep the potato from shrivelling wdien exposed to the air and 

 so are more dependent upon the earth for protection, but they 

 are tubers none the less ; the last step in the evolution of an un- 

 derground method of vegetative reproduction. 



HELIANTHUS TUBEROSUS 



