The Nature and Origin of Stipules. 39 



another is the family of the Rubiaceae with anomalous stipular 

 development in the group of the Stellatae. The oaks also, though 

 of lower organization, are an advancing type and still actively 

 undergoing differentiation as evinced hy the close relationship and 

 difficulty of determination of the species of any given group. In 

 this genus all but the upper part of the primitive leaf has disap- 

 peared by degeneration even in the earliest stages represented in 

 embryonic leaf-development, and the well developed stipules are 

 distinct and separate from the very base of a developing shoot. 

 Not until the fifteenth node, in Quercus rubra L. (fig. 39), is there 

 any appearance of lamina. The apical portion of the protophyll 

 must however be regarded as potentially present between the 

 stipules at their base. It begins its development unusually late 

 in the series and exhibits several stages, of which the twentieth 

 leaf (fig. 40) is illustrative, before reaching adult size. The axial 

 portion of the protophyll being aborted, the petiole, here again a 

 short one, is formed by the contraction of the basal part of the 

 lamina itself. The case of Fagus is very similar, but the lamina 

 appears as earl y as the eighth node (fig. 41), indicating a less de- 

 gree of specialization. In related genera a different course has 

 been followed. The lamina develops still earlier and the stipules 

 of the lowest nodes are united, separating only on the appearance 

 of the first accompanying lamina. 



In the family of the Juglandacese the genus Hicoria furnishes 

 a very interesting example. The lower foliar organs are of the 

 primitive type with an unusual development in size in some 

 species. The transition to the adult leaf-form is commonl}' 

 rather abrupt, but I have observed, in both Hicoria alba (L.) 

 Britton and H. microcarpa (Nutt.) Britton, the frequent occur- 

 rence of intermediate forms, the lateral portions remaining as 

 typical adnate stipules (fig. 42). 



I have not seen the typical representation of embryonic leaf-de- 

 velopment better exemplified than in the case of Baptisia tinc- 

 toria (L.) R. Br. where at a glance one is struck with its clear- 

 ness. It is also especially full and accurate as occurring in the 

 development of subterreanean buds. The first five leaves are ex- 

 tremely primitive, completely surrounding the node, though only 

 slightly developed on one side. The fifth (fig. 43) shows at its apex 

 a minute apical tooth, the beginning of the lamina which is farther 

 developed in the sixth leaf. In the seventh (fig. 44) the three leaflets 



