BOTANY OF LA SAL,IvE COUNTY. 11 



The writer has seen a change of from 20 deg. to -5 

 deg. in two and a half hours and from 22 to -15 deg. in 

 six and a half hours and from half past two p. m. to 7 

 a. m. the change was from 22 deg. to -22 deg. a range 

 of 44 deg. in sixteen and a half hours. The changes 

 from cold to warm are almost as rapid and range over 

 25 deg. or more from 6 a. m. to 3 p. m. The result is 

 a summer with many excessively hot, sultry days, the 

 heat being greater than at New Orleans at the same 

 time and much more oppressive, for there, there is 

 generally a fresh, breeze blowing and the nights are 

 cool and one can sleep very comfortably, while in L/a 

 Salle County there is often little or no wind and the 

 nights are as close and stifling as the days, and a win- 

 ter with many days as cold as at Minneapolis. 



The valleys of the Illinois, Pox and Big Vermillion 

 being from 150 to 240 feet below the level of the 

 prairie are warmer and in sheltered nooks, one there 

 often finds plants, especially, Sambucus pubescens, 

 putting forth buds two or three weeks earlier than 

 they do on the adjacent highland and blooming much 

 earlier, and hence some plants are confined to these 

 places, which seem especially calculated for their ac- 

 commodation. 



It should be noticed, however, that the lower parts 

 of the prairies are always the first to show the effects 

 of frost, the highest points being generally the last to 

 become brown and sere from its assaults. We have 

 seen the cotton plant, Gossypium herbaceum, in Farm 

 Ridge township long after the cornfields were brown 

 and ice as thick as window glass had formed more 

 than once on the pools of the lower country, lying on 

 either side of the ridge. It is also to be observed that 

 fruit trees on the ridge and near the bluffs bear more 

 regnlarly than those on the lower lands. The valleys 



