The Nature and Origin of Stipules. 41 



bipinnate condition (figs. 48-50). In this case it is remarkable 

 that the first appearance of the secondary leaflet is in the shape 

 of a small body with both the form and position of a stipel, with 

 the same small supporting vein and differing only in greater thick- 

 ness. These facts seem to give evidence sufficiently conclusive 

 that stipels are in reality rudimentary leaflets. That their de- 

 velopment is not confined to the Leguminosse is farther shown \>y 

 their characteristic occurrence in Staphylea trifolia L, 



Another frequent foliar variation among the Leguminosse is the 

 development of the phyllodium, which might be thought to have 

 some connection with stipules, but the presence of both together 

 in some genera disproves the idea.* The stipules in the Legu- 

 minosse often take the form of spines which serve for the general 

 protection of the plant. We have an example in the well known 

 Bobinia Pseudacacia L. (fig. 51). In some of the tropical Aca- 

 cias, as for example A. spadicigera C. & S. (fig. 52), they take the 

 form of enormous hollow horns which are appropriated as homes 

 by some species of ants.f 



Sambucus Canadensis L. presents another remarkable char- 

 acter. The leaves of the vernal shoots from subterranean buds 

 are furnished with stipules of the same form and in the same po- 

 sition as those of Sambucus Ebulus L., but smaller. There are 

 four of them at each node, they are ovate or nearly orbicular in 

 form, small, rather fleshy and persist but a short time. Each is 

 supplied with a small vascular bundle, originating as a branch of 

 the nodal girdle which connects the leaf-traces. These facts 

 give evidence of the close relationship of these two species of 

 Sambucus, and of the characteristic presence of stipules in the 

 ancestral form. In Sambucus Ebulus L., they are still typically 

 developed, but in our species have become so far vestigial as to 

 appear only in connection with the early leaves of shoots from 

 subterranean buds, an additional evidence of the importance of 

 the leaf-forms successively developed from such buds, in their 

 bearing on the evolutionary development of modern adult forms. 



If now we turn to the family of the Rosacese we shall find many 

 illustrative examples of the same facts as those born out in the 

 case of Baptisia tinctoria (L.) R. Br. But it frequently happens 

 that basal degeneration does not take place or is only partial, re- 



* Bentham and Mueller. Flora of Australia, 2: 304. 1864. 

 t Belt. Naturalist in Nicaraugua, 218. 1874. 



