102 ROBERT TRACY JACKSOX OX 



ledons are not shown on the specimens. In later growth the leaves are trifoliolate. In 

 the adult the leaves are very variable in outline and degree of division, having from three 

 to seven leaflets. Occasional simple leaves are also seen as reversions. The terminal and 

 lateral leaflets vary much in outline (PL 18, fig. 3G), being ovate, denticulate, trilobed, 

 or even twice pinnate. When trilobed, as in the terminal leaflet of the figure, they bear 

 considerable resemblance to the nepionic leaves of the seedling. A sucker from the base 

 of an adult (PL 18, fig. 35) has first a simple trilobed leaf, like the young, also like the 

 simpler fossil and living species of maples. The second leaf of this sucker is trifoliolate. 

 In two other suckers, two simple trilobed leaves precede the first compound leaves. The 

 seedlings, suckers, and often' the terminal leaflets, therefore, show distinctly reversionary 

 characters. 



Gymnocladus disicus. In the Kentucky Coffee-tree {Gi/mnocladus disicus L.) 

 the leaves (PL 18, fig. 37) are very large and twice paripinnate. The proximal end of 

 the leaf, however, has two, three, or four simple leaflets, commonly four. The total num- 

 ber of leaflets on large leaves counted varied from seventy-five to one hundred and 

 seventeen. I have not seen seedlings of this species, but it suckers freely from under- 

 ground roots. The sucker (PL 18, fig. 38) has once compound leaves, composed of few 

 leaflets, four in the specimen figured, which was the smallest number seen. Later leaves 

 on the sucker rapidly increase in the number of leaflets and soon become twice compound. 

 From evidence in other types, it is probable that the nepionic leaves of the seedling are 

 very similar to the first leaves of the sucker. In many cases, as noted, the distal portion 

 of the leaf repeats the form of nepionic leaves. It is interesting to note that here the 

 proximal portion of the adult leaf resembles the once pinnate condition of the leaf of the 

 sucker and presumably of the seedling ; in so far it is reversionary in character. 



Gleditschia triacanthos. In the Honey Locust {Gleditschia triacanthos L.) the 

 seedling has thick, fleshy, rounded cotyledons (PL 18, fig. 39). They are auricled at the 

 base, nearly embracing the stem, as shown in Fig. 39a. The nepionic leaves are alter- 

 nate, once compound, paripinnate. The first leaf has numerous leaflets, sessile, not quite 

 opposite one another. Succeeding leaves are similar, but progressively larger, with more 

 leaflets. The leaves of the adult are once or twice paripinnate. The twice pinnate 

 leaves are borne on the new growth at the ends of tlie branches; but the leaves of the 

 old wood or proximal portion of the branches are once pinnate. The old wood, therefore, 

 bears the more primitive, the new wood the more specialized type of leaf. Occasion- 

 ally a few once compound leaves are seen on the new wood as a reversionary variation. 

 The distal end of once pinnate leaves or the end of the second division of twice compound 

 leaves repeats the form of the nepionic leaves of the seedling. It is noted in many cases 

 that the distal end of adult simple or compound imparipinnate leaves closely resembles 



