-^Q^ ROBERT TRACY JACKSON 



Of leaves during growth. This is reproduced here by the courtesy of Messrs D Apple- 

 ton and Company. Lubbock shows that in the seedling the cotyledons are first sessile, 

 oblono-orbicular, auricled at the base, and with an emarginate tip (Fig. 1). in latei 

 growtl a slight constriction appears near the base on either side. " This basal poHion 

 increases much more rapidly, while the growth of the terminal portion (which is, m fact, 

 the oric/inal cotyledon) becomes gradually arrested." (Fig. 2.) "In its ^^'f J^J^ 

 (fie. r.31) the new portion is both broader and longer than the true cotyledon, and d^ers 

 from it not only in the crenations, but in the possession of a more conspicuous midrib 

 and rather stiff hairs. Not only is this basal portion interesting in its mode of develop- 

 ment, but also fron. its similarity to the subsequent leaves. In fact, * * * it may be said 

 that we have a compound structure formed of a leaf at the base, terminated by the coty- 

 ledon " He describes similar changes in cotyledons of species of Clarkia and Oenothera. 

 These cases are very interesting as cases of accelerated development, m which features 

 ordinarily originating later are shoved back into embryonic stages. They are especially 

 interesting to us here, however, as illustrating localized stages in development m the 

 ontoo-enesis of a leaf, showing that in progressive periods of its growth it may actually 

 acquire features which make the characters of the leaf an epitome of the development 

 of the type. Special attention is called to the fact, that the new additions are made to 

 the proximal portion of the leaf, the distal portion retaining its original characters 



Patsia japonica. The seedling of Fatsia japonica Decne and Planch. {Araha 

 sieboldii Hort.) (PI. 18, fig. 41) has obovate rounded cotyledons. Succeeding nepionic 

 leaves are alternate, the first leaf is broadly ovate, the second cordate, both finely 

 dentate, and the third leaf is trilobed. The first two leaves closely resemble the leaves of 

 the same stage in Aralia edulis Sieb. and Zucc, as figured by Lubbock ('92). The adult 

 leaves of that species are large and bipinnate. In adult Fatsia japonica the leaves are 

 large, palmately deeply cleft, serrate (PL 18, fig. 40). In two plants some six feet high 

 (raised from seed), which were cut down nearly to the ground, suckers were thrown out. 

 In the sucker (PI. 18, fig. 42), the first two leaves are in one case broadly cordate, 

 dentate, in the other trilobed, both resembling closely the nepionic leaves of the seedling. 

 It should be noted, however, that in the sucker the first leaf is trilobed, the second cor- 

 date whereas the reverse order is the condition of the seedling. Aralia notata Lx. of 

 the Cretaceous is trilobed and closely resembles the trilobed leaf of the seedling and 

 sucker of Fatsia japonica. 



Hedera helix. In the English Ivy (Hedem helix L.), the seedling (PI. 18, fig. 43) 

 has two broadly ovate cotyledons. Succeeding nepionic leaves are alternate. The first 

 nepionic leaf is broadly ovate, with only a slight indication of a lobe on one side. The 

 second leaf is also broadly ovate, and has a slightly developed lobe on either side. The 



