32 JOURNAL OF THE ARNOLD ARBORETUM (vol. iv. 



myself found fruit and leaves of Quercus nigra in deposits of the same 

 period near Palestine in eastern Texas. And while the little known 

 Quercus arkansana has not as yet been recorded in a fossil state its characters 

 and the circumstances of its distribution suggests the possibility at 

 least that it may be a surviving representative of an ancient form perhaps 

 ancestral to both of its nearest living allies. Somewhat similar is the case 

 with regard to the Nutmeg Hickory (Carya myristicaeformis Nutt.), 

 which, as mentioned by Professor Sargent (Botanical Gazette, LXVI, 

 233), is the only living species connecting two quite distinct sections of 

 the Hickories. Its comparative rarity and peculiar distribution would 

 also indicate that it is an ancient and disappearing species that may 

 formerly have been much more abundant. It is of course quite im- 

 possible now to trace except in the most general way the complex 

 succession of influences that resulted in the present composition and 

 distribution of our forests. In their earlier stages they were probably 

 profoundly affected by the advance and retreat of the glaciers, or by 

 oreogenic movements with consequent changes in drainage systems or the 

 obliteration of great inland bodies of water, or by the appearance or 

 severance of land connections or barriers, any of which might result in 

 profound climatic changes. In response to these influences the move- 

 ments of advance or retreat would proceed until they become in- 

 operative or perhaps were reversed by some new development. In the 

 progress of such movements, especially along lines of retreat, many 

 stragglers and small colonies would be scattered and make stands in spots 

 particularly favored by topography, soil or other local conditions, and as 

 the turning point was approached these would naturally have become 

 more numerous. In the course of such fluctuations cross currents must 

 often have met and so brought together diverse elements from widely 



separated sources. 



In localities like the one we are considering, in the Red River valley 

 near Fulton, Arkansas, there seems to be evidence that something of this 

 this sort has taken place. Indeed such shiftings and minglings have doubt- 

 less occurred many times in all parts of the forest area, the only difference 

 being that in certain places the effect was more marked and the evidence 

 has been better preserved. Among the influences that we may recognize 

 at present as accounting for the richness and diversity of the flora and the 

 preservation of a number of unusual species in this locality are the proxim- 

 ity of the great river and the character and position of its valley, lying as it 

 doesjustsouth of the semi-mountainous Ozark region; the diversity of drain- 

 age conditions and soils, and especially the presence of the light marly sands 

 and the rather peculiar ridge and ravine topography developed in this 

 formation. Just what, however, were the influences or sequence of events 

 that account for the bringing together of this rather remarkable collection 

 of ligneous plants in so small a space it is also impossible to deter- 

 mine. In its earlier stages it was doubtless involved with those great 



