116 ROBERT TRACY JACKSON ON 



The leaf-clusters of the White Pine are enclosed in a ver}' short sheatli at the l)ase (PL 21, 

 fig. 81a); from mutual pressure they have taken on a triangular form (Figs. 81a, b) , and 

 the angles have saw-like teeth (Fig. 81a, c) , as in the Pitch Pine. 



In seedling jjines the duration of the nepionic character of primary leaves varies 

 greatl}^ according to the species. Such nepionic characters may appear later in special 

 localized growtlis under certain conditions, as described, but this again varies with species, 

 not being a character common to all pines. 



PiNUS EESiNOSA. In seedlings of Piniis resinosa Alton, the features dii^er from 

 those of other pines observed. The specimens were grown at the Arnold arboretum, 

 one of them has 7 cotyledons, a second has 6 ; they are quite large, measuring 2 cm. in 

 length. The primary leaves are unusually long, measuring 27-30 mm., and have fine ser- 

 rate teeth on the lateral borders as in other species. The cluster-leaves are in twos, 

 fiat on their apposed borders, curved on their outer sides, with rows of fine serrate spines 

 as in primary leaves. The first cluster of leaves in the seedling is in the axil of a pri- 

 mary leaf within 2 mm. of the cotyledons. Other axillary bundles occur throughout the 

 length of the axis, which in the larger specimen measures 25 mm. above the cotyledons. 

 The larger part of the primary leaves, however, do not bear axillary clustei's. This spe- 

 cies is peculiar in the size and luxuriance of the primary leaves, in the early introduction 

 of bundles of leaves, and in the relatively small number of such bundles to the number 

 of primaries during early growth, 



Larix. Of the Larch I have only seen one young seedling which was kindly sent 

 me by Mr. Charles E. Faxon. This seedling, Larix occidentalis Nutt. (PL 21, fig. 82), 

 has five cotyledons, quite similar to those of the pine. Succeeding the cotyledons the 

 nepionic leaves are thickly distributed on the ascending axis, but not so thickly as in 

 the pines. These nepionic leaves are narrow, linear, acuminate distally. In the adult 

 Larch, as represented by Larix europaea DC. (PL 21, fig. 8-3), the leaves are given off 

 in dense clusters on the old wood. In the new wood of the current season's growth, on 

 the other hand, there are no clusters, but the leaves are given off singly along the axis, 

 as in the seedling. The cun-ent season's growth of this tree, then, resembles closely the 

 nepionic growth of the seedling. A similar condition has been observed in other cases, 

 where the new growth of the current year resembles the young. This is especially 

 marked in Ampelojjsis tricus2ndata as described. • 



JuNiPERUS viRGiNiANA. In the Red Cedar {Juniperiis virginiana L.) the later 

 stages in development and the features of the adult are very striking. Young seedlings 

 were found in comparative abundance near adults in July and August, both at Martha's 

 Vineyard and Milton, Mass. The seedling. Fig. 4, has two relatively broad, strap-shaped 

 cotyledons, which are thin and very fugitive. While the number of cotyledons is variable 



