400 NATURE-STUDY REVIEW [12:9— Dec, 1916 



No transitional forms between the three-lobed and two-lobed 

 leaves were noted on the same tree. The latter apparently 

 increases in number as the three-lobed forms decrease, and are 

 associated mostly with the single-lobed leaves, being about equally 

 distributed between the younger and older twigs. They are 

 rarely found at the top of the tree. Evidence that the available 

 amount of light may play some part in the distribution of leaves 

 is found in the fact that the great majority of observed seedlings 

 growing in the shade develop the three-lobed terminal leaves, 

 and a large proportion of the remainder one-lobed or two-lobed 

 leaves in combination. Contrast is offered by a statement made 

 in a standard American textbook of botany — "In Sassafras, 

 almost any leaf may be entire or variously lobed, apparently 

 without relation to transpiration, nutrition, etc." 



Bearing in mind the foregoing statement, an attempt was made 

 to ascertain experimentally the relation of amount of light as 

 to kind of leaves developed. This year's twigs bearing only one- 

 lobed forms were tied back into shaded positions. Of ten such 

 cases, three twigs produced isolated, three-lobed leaves. In another 

 lot of the younger twigs bearing only one-lobed forms, the leaves 

 were stripped from the twigs, and these too tied back in the shade. 

 Only one twig of this lot responded, producing two two-lobed and 

 one three-lobed leaf. A consistent explanation of this fragmentary 

 evidence would be that the formative elements for three-lobed 

 leaves in the twigs are stimulated to produce those forms. A more 

 positive point brought out is the lack of proliferating power in the 

 trees under the condition of the experiments — when compared 

 with other forms possessing divided leaves as the mulberry — the 

 majority of mutilated twigs at this season, early August, not 

 renewing their leaves. The writer is indebted for use of material 

 to Mrs. W. G. Gibson of Avalon, Pa., and Prof. W. J. Stevens, 

 Field School, St. Louis, Mo. 



N. M. Grier, 



Central High School, 



St. Louis, Mo. 



