155 



The coffee bean is a marked example. A clump of six trees, 

 50 feet in height, occurs on the gravelly border of Apple river 

 bottom, two miles below Millville, and no others are known 

 until the bluffs of the Mississippi are reached, 25 miles north- 

 west. Morns rubra, the mulberry, has exactly the same dis- 

 tribution. Carya illinoicnsis, the pecan, occurs at one place on 

 the elevated bottom of the Mississippi river, a single specimen 

 90 feet in height, and 3.5 feet in diameter, in the midst of a 

 woodland of elm and maple. Betula alba is occasional along the 

 bluffs of the Apple river, and again on the summits of Benton 

 mound, at 300 feet greater altitude (1200 feet above the level of 

 the sea,) and 10 miles distant. Honey locust exists as few 

 specimens on sand prairie ; Ulnius racemosa is seen only on the 

 west branch of Apple river. It would be a difficult task to ex- 

 plain the origin of these species, some seemingly from the south, 

 and one or two from the far northeast. 



Enough has been said to give a glimpse of the tree distribu- 

 tion of the region, and the grouping that seems to be rational 

 and most easily accounted for. Errors of judgment there may 

 be, but the points of distribution are facts that I have sought 

 the best explanation for, from the data at my command. 



LIST OF TREES OF NORTHWESTERN ILLINOIS. 



1 Finns strobus, 



2 Juniperus virginiana, 

 S Salix nigra, 



4 Salix amygdaloides, 



5 Salix lucida, 



6 Salix longifoUa, 



7 Salix discolor, 



8 Salix rostrata, 



9 Populus tremuloides, 



10 Populus grandidentata, 



11 Populus deltoides, 



12 Juglans cinerea, 



13 Juglans nigra, 



l-'f Carya illinoensis, 



15 Carya ovata, 



16 Carya glabra, 



11 Carya cordiformis, 



18 Ostrya virginana, 



19 Carpinus caroliniana, 



20 Betula alha, 



21 Quercus alba, 



22 Qucreus macrocarpa, 



23 Quercus picolor, 



2k Quercus muJilenbergii, 



25 Quercus rubra, 



26 Quercus palustris, 

 2~i Quercus coccinea, 



28 Quercus velutina, 



29 JJlmus fulva, 



30 Ulmus americana, 



31 Ulmus racemosa, 



32 Celtis occidentalis, 

 S3 Morus rulra, 



S-'f Hamamelis virginiana, 



35 Platanus occidentalis, 



36 Pyrus coronaria, 

 31 Pyrus ioensis, 



38 Amelanchier canadensis, 



39 Crataegus punctata, 

 J/O Crataegus toinentosa, 

 J/l Crataegus mollis, 



If2 Crataegus macracantha. 



