20 The Nature and Origin of Stipules. 



" When stipules are present [in Helianthemum~\ the petiole is 

 always very narrow, semiterete, and tapered to the base. Where 

 they are absent the leaf is often sessile and, whether or not, its 

 base is always dilated and concave on the inner face, completely 

 enclosing the bud up to a certain stage of its development." 



The presence of stipules in the lower imperfect leaves of Ailan- 

 thus glandulosa Desf. is noticed, though the family of the Sim- 

 arubiacese has been described as exstipulate. In Ribes sanguin- 

 eus, Pursh. the bud-scales are described as consisting of the 

 dilated base of the petiole, the lamina being represented by a 

 small black point. " One or two succeeding leaves bear a small 

 lamina sessile on the sheath, which is wholly adnate to the thin 

 dilated base of the petiole and membranous, especially outside of 

 the three vascular bundles. The next one or two have a well- 

 developed lamina, and the sheaths partly separated from the 

 petiole and corresponding to stipules. Farther up the stipular 

 sheaths are shorter and wholly adnate to the petiole." 



The form and function of the stipules in a large number of 

 species are described. 



I^esquereilXj L.. — IT. S. Geol. Surv., Monog. No. 117 : Geology of the 

 Dakota Group. 1892. 



Well-developed stipules of a species of Betulites from Kansas 

 are described (p. 65) as having been found in their original con- 

 nection with the leaf, and the discovery of leaves of a Crataegus 

 with large undoubted stipules, from the Devonian of Wyoming is 

 mentioned (p. 254). Speaking of a leaf of Aspidiophyllum 

 (p. 232). Professor Lesquereux says, "the basilar appendage or 

 pelta is like a primordial form of stipules, as in Platanus 

 basilobata Ward of the Laramie group of Wyoming, P. appen- 

 diculata Lesq. of the auriferous gravels of California and definitive- 

 ly in P. occidentalis L. of the living flora." 



Henslow, Rev. <2eorge. — On a Theoretical Origin of Endogens from 

 Exogens. Jour. Linn. Soc. Lond. 29: 485-528. 1893. 



The absence of vascular bundles in certain stipules is noted 

 (p. 494). 



HolJick. Arthur. — Wing-like Appendages on the Petioles of Lirio- 

 phyllum populoides Lesq. and Liriodendron alatum Newb. Bull. Torr. Bot. Club, 

 21: 467-471. 1894. 



These peculiar wing-like appendages are described and figured. 

 Their similarity to the appendages in fossil species of Platanus as 



