402 



TEE AMERICAN NATURALIST [Vol. LV 



up to a certain point a progressive and parallel increase 

 in the size of the plant and in the size of the primary 

 meristems of its axes; but that after this point is reached 

 meristem size remains constant and further increase in 

 body size is not accompanied by any increase at all in 

 that of the growing point. 



5. Favorable material to test this hypothesis directly 

 was afforded by twigs and leaves of Acer saccharum. 

 The correlation between the blade volume of a given leaf 

 pair and the cross-sectional area of the pith of the in- 

 temode below (used as an index to the size of the grow- 

 ing point from which the leaves had developed) was 

 found to be high (+ .807 ± .024). 



6. It is therefore concluded that the size of a plant 

 organ (leaf, fruit or seed) is dependent not upon the 

 body size of the plant on which it is borne, but rather 

 upon the size of the growing point from which it devel- 

 oped. 



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2. Ewing, E. C. Correlation of Characters in Corn. CorneU Exp. Sta. 



Bu'l., 287: 67-100, 1910. 



3. Harris, J. Arthur. On the Correlation between Somatic Characters and 



Fertility. II. Illustrations from Phuscolus vulgaris. Amcr. Jour. 

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Exp. Sta. BuU. (New Haven), 171: 3-45, 1912. 

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Breeders Assoc. Rept., 7: lOl^-lls, UUl. 



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