1921] PALMER, THE FOREST FLORA OF THE OZARK REGION 219 



to the charts of the United States Weather Bureau. The precipitation 

 is well distributed throughout the year, spring and autumn being the 

 wettest seasons, while there Is often a short period of drouth in midsummer 

 or winter. Extending over about four degrees of latitude there is a per- 

 ceptible though not very marked difference in the mean average tenipera- 

 ture in the northern and southern extremes. In the vicinity of the Miss- 

 ouri River the average annual depth of snow is about 25 inches, while 

 along the Arkansas River it is scarcely a fourth of that amount; in the 

 former region wiater temperatures of from 15 to 20 degrees below zero 

 Fahrenheit are not infrequent while in the latter the zero point is seldom 

 passed. However, mild winters or a succession of them are not infrequent 

 at the north, while rarely in extremely cold winters the thermometer 

 falls below twenty minus there, and to ten or twelve minus at the 

 south; and it is, of course, these occasional low extremes rather than 

 the average temperature that limits the northward range of the less hardy 



species. 



The humid division of the Upper Austral life-zone, as defined and 

 mapped by the United States Biological Survey, embraces most of the 

 Ozark region, including all of the Ozark plateau and the higher portions 

 of the Boston Mountains. Agriculturally it is a country where the north- 

 ern cereals, forage crops, apples and small fruits abound, and in its more 

 fertile portions is particularly adapted to stock raising, dairying and fruit 

 growing. The timber industries consist of pine and hard wood lumber- 

 ing on a small scale in many sections, and of the wasteful production of 

 railway ties from the Oak-forests, Red Cedar (Juniperus virginiana L.) 

 is cut in considerable quantities in some places for posts, pencil and chest 

 lumber, and Hickory and Ash supply material for some local industries. 

 A small comer in Oklahoma and many tongue-like i)roiections up the 

 valleys of the larger streams on the southern and southeastern border is 

 included in the humid division of the Lower x\ustral zone. Here cotton, 

 watermelons, yams and peanuts compete wuth maize and other cereals 

 as staple crops and the heavier growth of forest and easier transport- 

 ation have in the past made lumbering and the manufacture of timber 

 products one of the leading lines of industry. Saw mills and plants for 

 the manufacture of barrel staves and other hard wood products still 

 operate at many places, but the industry is rapidly declining and the fer- 

 tile cleared land is now cultivated. Most of this humid division, however, 

 although broadly within the bounderies of the Ozark region is scarcely a 



part of it. 



In the composition and character of the forest flora there are no such 



clearly recognizable divisions as in the topography; but in the Boston 



Mountain area and in the southern part of the Ozark plateau adjoining 



it a number of species are found which disappear gradually northward; 



and generally speaking the forest growth over this portion is heavier, 



more continuous and richer in types than over the central, northern and 



especially the northwestern parts of the plateau. Ccmspicuous among 



