FLOWERING PLANTS AND FERNS OF INDIANA. 559 



AVERAGE PRECIPITATION IN INCHES.-FOURTEEN YEARS. 



Average. 



d 



— ' 



■— 

 ea 



i 

 < 



i 



June. 



>> 



3 

 < 



a 

 ® 

 on 



- 

 ° 



> 



o 



® 



Northern 



. . 2.49 



2.57 



2.52 



3.08 



4.47 



3.81 



3.07 



2.82 



3.11 



1.86 



3.46 



2.52 



Central 



.. 2.99 



3.09 



3.54 



3.98 



3.92 



3.11 



3.24 



3.21 



1.80 



4.01 



2.78 



Southern 



. . 3.64 



4.06 ' 3.95 



4.01 



3.96 



4 20 



3.55 



3.45 



3.20 



2.02 



4.47 



3.08 



SOILS. 



"The soils of Indiana may be roughly classified into three great 

 groups; viz., drift soil, residual soils and alluvial soils. The drift soils 

 are found in the northern three-fourths of the State, are extremely 

 varied in depth and character and are formed of a mass of heterogene- 

 ous material which was brought to its present resting place by a great 

 glacier or slowly moving sheet of ice, which thousands of years ago, 

 covered the area mentioned. 



"The residual soils are found in the counties south of the southern 

 limit of the glacier. They were formed, for the most part, in the place 

 where they are now found, by the decay of the underlying limestone or 

 sandstone rocks. The variety of materials entering into their com- 

 position is therefore limited, and they are, for that reason, among the 

 poorer soils of the State. 



"The alluvial soils are those of the river and creek bottoms through- 

 out the State. Gentle rains and earth-born torrents, little trickling 

 rills and strong streams are ever at work tearing down the soils and 

 underlying clays from every slope, and bearing them away to lower 

 levels. The small water-formed trench of to-day next year becomes a 

 chasm and ages hence a hollow, and the transported material is gradu- 

 ally deposited as alluvial soil over the so-called "bottom lands," which 

 are annually overflowed. 



"The drift soils which cover the northern and central portions of In- 

 diana, derived, as they were, from various primary and igneous rocks 

 in the far north — ground fine and thoroughly mixed as they were by 

 the onward moving force of a mighty glacier — are usually rich in all 

 the necessary constituents of plant food. Neither they nor the alluv- 

 ial soils require a large annual outlay for fertilizers as do the residual 

 soils of southern Indiana, over which the drift of the glacial period 

 did not extend."* 



•Blatchley— 21st Ann. Rep. Dep. of Geol.anrt Nat. Resour. of Indiana, 1896, pp. 21 



