172 



which 0. nitida came into the Stale. There is as much reason for regard- 

 ing the Illinois station as the westward extension of the Indiana station as 

 the reverse. 



The Water Locust or Thorn Tree (Gleditskt aquatica Marshall) is 

 found in a few localities in Gibson, Knox and Posey counties in sloughs and 

 cypress swamps. This is a northern and eastern extension of a definitely 

 southern species which must have entered our flora at a time when the 

 swamp areas of the river bottoms were practically continuous and which 

 has been able to maintain itself only in occasional deep river swamps 

 within our boundaries. In Indiana the species is both rare and local and 

 one which will, in all probability, soon disappear. 



One of the Hollies (Ilex decidua Walter) occurs occasionally in the 

 three southwestern counties, being invariably restricted to the borders of 

 ponds and sloughs near water courses. Although at times it forms fairly 

 dense thickets, it rarely, in our region, reaches tree size. The distribution 

 as given in Sargent's "Trees of North America," p. 618, is significant in 

 this connection : "Borders of streams and swamps in low moist soil ; 

 southern Virginia to western Florida in the region between the eastern base 

 of the Appalachian Mountains and the neighborhood of the coast, and 

 through the Gulf States to the valley of the Colorado River, Texas, and 

 through Arkansas and Missouri to southern Illinois: usually shrubby east 

 of the Mississippi River and only arborescent in Missouri, southern Arkan- 

 sas and eastern Texas." It is merely another instance in which an essen- 

 tially coastal form has found its way deep into the interior. When con- 

 sidered in connection with other cases, some of which have been cited, the 

 conclusion is almost inevitable — that the only adequate explanation is to 

 be found in relating it to the northward stretching arm of the Gulf of 

 Mexico. 



Pond-bush (Forestiera acuminata (Michaux) Poiret) is another spe- 

 cies strictly limited to Gibson, Knox and Posey counties where "it is found 

 in swamps, on the borders of ponds and on low river banks. It is very 

 tolerant of shade and is frequently found growing in a thick stand of tall 

 trees." 7 The Indiana stations represent the extreme northeastern limit of 

 this species, which extends westward to Missouri and south to Texas. In 

 Indiana it is ordinarily a shrub, at times forming almost impenetra- 

 ble thickets. It is impossible to determine from the data at hand as 

 to whether this is a western or southern form. In either case its habitat, 



'Dearn. Op. Cit. 342. 



