252 



UPPER MIOCENE FLORA OF (ENINGEN. 



[Ch. XV. 



poplars and willows, countless leaves of which became imbedded in 

 the mud. Together with them, at some points, a species of reed, 

 Arundo, was very common. 



One of the most characteristic shrubs is a papilionaceous and legu- 

 minous plant of an extinct genus, called by Heer Podogonium, of 

 which two species are known. Entire twigs have been found (a, fig. 

 180), with flowers, and always without leaves, the flowers having evi- 

 dently come out, as in the poplar and willow tribe, before any leaves 

 made their appearance. Other specimens have been obtained with 

 ripe fruit accompanied by leaves, as shown in the branch b, fig. 180. 

 In some specimens are seen the embryo and cotyledons, in others the 

 calyx and young fruit. The leaves resemble those of the tamarind, 

 but each pod contains only a single seed, whereas the pod of the 

 tamarind, an allied genus, contains many seeds. 



In fig. 181 we see a ripe seed-vessel of this plant, and on the same 

 thin slab a winged ant, c, Formica lignitum, Heer. Another species 

 of ant, also with wings, has been found associated with the same 

 Podogonium in fructification, from which fact Professor Heer con- 

 cludes that it ripened its seed, in summer, at which season alone 

 swarms of perfect male and female ants, having their wings fully 

 developed, make their flights. Such, for example, is the habit of the 

 living Formica herculeana, which comes very near to F. lignitum. 

 In the same slab, at d, is a portion of a beetle of the genus Hister. 



The Upper Miocene flora of OEningen is peculiarly important, in 

 consequence of the number of genera of which not merely the leaves, 



Fig. 182. 



Acer trilobatum, normal form. Heer, Flora Tert. Helv., pi. 114, fig. 2. Size $ diam. 



(Part only of the long stalk of the original fossil specimen is here given.) 



Upper Miocene, (Eningen ; also found in Lower Miocene of Switzerland. 



but, as in the case of the Podogonium just mentioned, the fruit also 

 and even the flower are known. Thus there are nineteen species of 



