CHICAGO AND VICINITY. 



29 



plains there may be found the mulberry [Morus rubra), the red bud 

 {Cercis Canadensis), the buckeye {/Esculus glabra), and the tulip {Lirio- 

 dendroii tulipifera). 



None of these trees are common in our district, and only Celtis 



niav be regarded as frequent. These relatively southern trees are 

 found not onlv along the Desplaines and its tributaries, where there is 

 supplied a continuous habitat along the river southward, but also along 



Fig. 14. — Flood plain of the Calumet river near Chesterton, showing the beginnings of ter- 

 race formation, indicated more by the falling elm than by the topography, 



the Calumet and its tributary, Thorn creek. The occurrence of the 

 tulip is full of interest, since it has been found thus far chiefly (perhaps 

 onlv) in the vicinity of the dunes. Its occurrence has been noted 

 especially at Chesterton along a small stream which empties into Lake 

 Michigan at that point; the tulip has also been found away from 

 present streams, but apparently in old valleys whose streams have been 

 diverted by dune activity. The confinement of these southern trees to 

 flood plains is not strange, since in such habitats are given the most 

 congenial conditions that can be found in our area. 



The vegetation on flood plains is not always as described above. 

 Sometimes meadows are found instead of forests; this condition is par- 

 ticularly well shown along Thorn creek. Fig. 18 shows a stretch of 

 meadow of this type. Besides various grasses, such as Poa pratensis 



