216 Trans. Acad. Sci. of St. Louis. 



All examination of the literature shows that more of these 

 deviations from the normal structure have been reported for 

 G. triacanthos than for any other species. This may, of 

 course, be due to its greater accessibility for study. Penzig, 

 however, in speaking of anomalies of the leaf, says: "Die 

 Laubblatter fast aller Gleditschien, besonders aber die von 

 Gl. triacanthos, zeigen sehr haufig eine Menge von Anom- 

 alien, welche von zahlreichen Autoren studiert und beschrieben 

 worden sind." This might indicate that G. triacanthos is 

 the member of the genus especially likely to show abnor- 

 malities. 



In the notes here presented I shall figure and briefly de- 

 scribe some variations from the usual structure noted in 

 thorns of Gledilschia during the summer and autumn of 

 1901. The material was collected in part in Douglas County, 

 Kansas, while I was doing work in the Botanical Laboratory of 

 the University of Kansas, and in part in the region in and 

 around St. Louis, and on the grounds of the Missouri Botan- 

 ical Garden, where the work has been put into its present 

 form. 



Sargent * says of the thorns of G. triacanthos : " The 

 spines, which are undeveloped branches, are three or four 

 inches long, simple or three-forked, terete, very sharp and 

 rigid, long pointed, thickened at the base, red at first and 

 bright chestnut-brown when fully grown ; they are produced 

 on some individuals from above the axils of all the leaves, 

 and sometimes in large numbers on the trunk and main 

 branches, but are wanting or nearly wanting in others." 



The thorns are usually nearly terete as Sargent describes 

 them. Some are found, however, which are very much 

 flattened. Such a case is shown in fig. 26. The branches, 

 when present, on these flattened thorns are also frequently 

 considerably flattened. 



The branch of the thorn, when present, is subtended by a 

 small but distinct scar, indicating the presence of a foliage leaf 

 on the thorn before it became of such a specialized character 

 as it is at present. This scar is also present in G. aqnatica. 



The production of thorns from adventitious buds on the 



* Sargent, I. c. 



