8 UNIVERSITY OF MISSOURI STUDIES L^5'^ 



ial collected. Practically the main portion of the existing veg- 

 etation, with the exception of the ligneous element, has come 

 into being during this period. The most aberrant years have 

 been 1901, when the precipitation was but one-half of the normal 

 amount, and 1904, which was the coldest and most backward 

 year under review. The sudden extremes, especially as to tem- 

 perature in winter, and as to precipitation in summer and 

 autumn, are peculiarly trying to the vegetation. Snows, in gen- 

 eral, soon thaw, and plants thus undergo a severe process of 

 alternate freezing and thawing in winter and early spring. 



The winds are strong and leave a marked impress upon 

 the vegetation. Thus the trees are round-topped, and the Amer- 

 ican elm, Ulmus Americana, for instance, seldom exhibits that 

 graceful dichotomus forking so characteristic of it in Michigan 

 and New England. The strong winds also favor the distribu- 

 tion and multiplication of such plants, notably the composite, 

 as have seeds fitted for wind dispersal. The winds also dry the 

 surface of the ground quickly after showers, and such plants as 

 the heaths and the orchids which require a soil uniformly cold 

 and soggy, are absent almost entirely. 



The appended tables, compiled from the annual summaries 

 of the Missouri section of the climate and crop service of the 

 United States Weather Bureau, will furnish the data requisite 

 for an understanding of the climate of the region. 



