DESCini'TION OF THE SrECIHS. 299 



iiiitJl the lowest pairs are sliurt-petioled ; midrib and nerves as seen on 

 tlie under side prominent and sharply defined ; midrib stout at base, but 

 towards the sunnnit rapidly attenuated ; lateral jjrimary nerves going off 

 ])innately at uniform and nearly equal intervals, proportionally very strong, 

 at first inclining slightly forwards, and then three-fourths of the distance 

 to the margin bending abruptly forwards at nearly a right angle, to form a 

 bow-shaped, strong nerve, which connects with the next primary at the 

 angle made by it, thus forming a series of arches ; this marginal nerve and 

 the primaries send off nearly at right angles a series of branches which are 

 ])roportionally very strong and distinct, forming the primary reticulation. 

 They unite nearly at right angles, and form four to six sided primary meshes; 

 the ultimate meshes are of the same general character, but smaller. 



Localities : 72d mile-post ; bank near Brooke ; White House Bluff. 



This is the most abundant angiosperm at the last-named locality. It 

 is very common at the two Brooke localities, but is not so abundant there 

 as S. mafjnifoJia. This plant is very variable, and shows a curious fluctua- 

 tion between odd and abruptly pinnate leaves and an alternate or opposite 

 arrangement of the leaflets, as if the habit of the plant was not yet fixed. 

 Plate CLII, Figs. 1, 4, seems to give the normal mode of arrangement of 

 the leaves ; i. e , they are odd-pinnate, with the lower leaves in pairs. In 

 none of the species, however, does the odd or abruptly pinnate mode of 

 arrangement of the terminal leaves seem to mean anything or to he fixed. 



1 have given a number of figures of abnormal forms of this plant to 

 illustrate its variability. PI. CLIV, Fig. 2, shows union of the three 

 terminal leaves and the decurrence of the two outer or lower ones by 

 means of a vei-}' wide wing. Tlie next lower pair of leaves are narrowly 

 decurreut and normally paired. Fig. 4 of the same plate shows the 

 decurrence of the uppermost leaves, but the leaves next below are not 

 paired, and are unequally winged. The next lower leaf stands alone and 

 the stem is quite- flexuous. Fig. 3 of the same plate shows two terminal 

 leaves united and decurreut to the next lower one on the left-hand side, 

 which is single, and uniting with it at base. On the right-hand side the 

 terminal leaf on that side is decurreut to the paired leaves below, witli 

 which, however, it does not unite. PI. CLV, Fig. 4, shows a terminal 



