94 STUDIES IN GEOLOGY, No. i 



Family MIMOSACE^ 



Genus Acacia WILLDENOW 



Acacia uninervifolia ENGELHARDT 



PLATE VII Figs. 4, 5. 



Acacia uninervifolia Engelhardt, Sitz. Naturw. Gesell. Isis in 

 Dresden, 1894, Abh. i, p. n, pi. i, figs. 10, u, 20. 



Berry, Proc. U. S. Natl. Mus., vol. 54, p. 129, pi. 15, figs. 14, 15, 

 1917. 



Description. Leaflets or phyllodes sessile, somewhat 

 variable in size, slightly or not at all inequilateral, lanceolate 

 to linear lanceolate in outline, with an equally acuminate 

 apex and base. Margins entire. Texture coriaceous. 

 Length, ranging from i to 2.25 cm. Maximum width, in 

 the middle of the leaflet, ranging from i to 3.5 mm. Mid- 

 rib relatively stout and prominent on the lower surface of 

 the leaflets. Secondaries thin, numerous, regularly spaced 

 and subparallel; about 15 pairs diverge from the midrib 

 at angles of about 45, curving regularly upward and 

 Ultimately tamptodrome. Tertiary venation obsolete by 

 immersion. 



This species is common at Potosi and also at Corocoro. 

 It was described by Engelhardt in 1894, who compared 

 it with the phyllodes of the existing Acacia pwadoxa De 

 Candolle. Engelhardt's figure 20 shows a relatively shorter 

 and wider form and may represent a leaflet of Mach&rium 

 eriocarpoides Engelhardt. 



The present species is similar to Mimosites Hngelhardti 

 Berry and Mack&rium eriocarpoides Engelhardt which 

 occur at both Potosi and Corocoro. It is relatively longer 

 and narrower than any of these but all may really represent 

 the variable leaflets of a single botanical species of legumi- 

 nous tree. Since they are named it has seemed best to let 

 them stand, although it appears obvious that the species 

 of Leguminosce represented in these Pliocene floras of 

 Bolivia have been excessively multiplied and several are 

 connected by intergrading forms. 



