IOWA ACADEMY OF SCIENCES. 55 



stems, leaving only the bench-roots, but in many places, for 

 example in Crawford and other counties, these little oaks have 

 now been unmolested by fires for quite a number of years, yet 

 they have not grown appreciably in exposed situations. The 

 stunted condition of the plants is probably due chiefly to the 

 action of winds. In their efforts to resist the strong, and often 

 hot and dry winds, the plants fortify themselves by pro- 

 ducing thicker walled cells, and stronger layers of cutin, thus 

 turning some of their energy aside for this purpose, with the 

 result that their general vigor is diminished, and if they sur- 

 vive they remain dwarfed. 



All this suggests, too, that trees are found along our eastern 

 streams largely because they are protected against summer 

 winds, and not so much because there is more moisture in such 

 situations. 



The isolated groves of the state are almost invariably, at 

 least in part, upon some knoll or ridge where they were able to 

 gain a foottiold and to maiutaia themselves because sheltered 

 from the southwest winds,* wherever there are elevations 

 which oifer such protection, whether upon the otherwise flat 

 drift areas, or in the regions covered by loess, there groves are 

 likely to appear. 



In further corroborative testimony it may be noted that the 

 efforts at tree planting in the western part of the state are not 

 always successful. Groves do not flourish except where pro- 

 tected. Walnut, ash, etc., do well in sheltered places or in 

 thickets, but if grown in rows or singly in exposed places they 

 soon die. f 



That fruit treas and smaller plants are benefited by a pro- 

 tecting wind-break, has long been known to the farmers of the 

 prairies. That our forest trees are equally benefited by such 

 protection is undoubtedly true. It has been noted "that a 

 tree will die, where a forest will live. "| 



Numerous instances might be cited from the author's own 

 observations in northwestern Iowa, in which trees planted in 

 single rows have failed, while upon the same tract, with the 

 same soil, the same species have flourished when grouped in 



*Sach are Oooa Grove In Winnebago county, smaU prairie groves in most of the 

 nortliwestern counties, tlie vicinity of Pilot Mound in Winnebago county, the groves 

 along the Des Moines river in Emmet county, etc. 



+ The Cottonwood is an exception, as It grows better when not in groves, and Is ' 

 therefore, superior in some places for wind-breaks. 



* Report of the U. S. Dep't of Agrl., for 1889, p. 276. 



