50 Cincinnati Society of Natural History. 



The graceful leaves of the walnut ; the rich glossy leaves of 

 the oak ; the beautifully serrated leaves of the chestnut ; the 

 truncate leaves of the Liriodendron ; the conspicuously lobed 

 leaves of the Liquidamber, and hosts of others, sway in unison 

 with the breeze, exciting both interest and admiration. But, 

 turn from the trees to the tiny seedlings round about ; how 

 different are their leaves from those of the great parent trees 

 which tower above them. Instead of the frond-like, pinnate 

 leaves, the seedling walnut at first bears only simple ones. 

 The serratures on the first leaves of the seedling chestnut are 

 mostly wanting; the tiny oaks bear lobeless leaves. In the 

 seedling Liquidamber, the first pair of leaves above the 

 cotyledons (Fig. i) are very different from those of the 3'oung 

 tree (Fig. 2). 



The first pair of leaves above the cotyledons, in the seed- 

 ling Liriodendron (P'ig. 3), vary quite as much from the typical 

 leaf (Fig. 4), the first leaves of the seedling being always 

 less complex than those of the adult plant. 



The variation in the leaves of herbs follows this same trend. 

 Take, for example, Trillium grandiflorum, which, at maturity, 

 or in the adult form, bears three leaflets. The little seedling 

 we find with but a single leaf, which is borne upon a long, 

 slender petiole or rootstalk (Fig. 5). It climbs no higher 

 during the first year's growth than this stage, with the single 

 leaf. The second year it bears two leaflets (Fig. 6), but not 

 until the third year do we find the plant with the normal 

 three leaflets. The common mandrake or May apple, Podo- 

 phyllum peltatum, we may take as another example of the 

 same law of development. The frail seedling during the first 

 year bears but the cotyledons ; two simple, entire, oval leaves 

 (Fig. 11). The second year a pair of larger, irregularly 

 notched leaves are produced (Figs. 8, 9, 10), which, perhaps, 

 may be considered as partially foreshadowing the adult form. 

 It is not, however, until the plant is three years old that it 

 bears the common peltate leaf (P'ig. 12). 



What more clearly illustrates the development of the simple 

 to the complex? vSpcncer says: "It is a law of heredity, 

 that the immature }oung resemble their remote ancestors, 

 while the adult reseml^k'S the immediate progenitors." 



