WINTEE MEETING. 327 



all from Manhattau. Those from the Missouri Botanical Garden for 

 1894 were taken by Prof. J. 0. Whitten and Mr.|E. Mische, at that time 

 a garden pupil; the others by the writer, with the assistance of many 

 of the garden pupils. , 



To illustrate the annual variations in the time of flowering, the 

 appended diagrams (plates 1-3) were designed. The vertical lines 

 represent the years, and the horizontal dotted lines every second day 

 beginning with the earliest date of flowering. A few plants from the 

 Missouri botanical garden list wpre selected for plate 1, and from Man- 

 hattan and Ames for the two following plates respectively. Knowing 

 the date that each plant blossomed during the different years of the 

 period, curved lines are drawn through points where the lines repre- 

 senting these dates intersect, and the name of the plant placed at the 

 end of the line. The direction of the line not only gives the actual 

 time for each year, but shows the yearly as well as extreme variation 

 that each plant reaches during the entire period. It will be observed 

 that the variation is much greater with some plants than with others, 

 showing that some respond more quickly to certain climatic conditions. 

 Again, one plant may blossom earlier than another one season and later 

 the following season. Take for example, Forsythie niridissima and 

 Dirca palustris. In 1895 the former appeared thirteen days later than 

 the latter, whereas in 1896 the former was seven days earlier than the 

 other. For these apparent inconsistencies it is very difficult to find a 

 reason. However, it seems to show that numerous elements must more 

 or less influence growth, and to find a reason each must be analyzed. 



Temperature tables for St. Louis and Manhattan, including mean 

 temperature for each day from February 1 to May 31 with the sums and 

 means for every 10 days as well as for each month, are given, together 

 with diagrams (plate 4) showing variations in the same manner as the 

 plant variations are indicated. 



The solid curved lines in this diagram represents the average tem- 

 perature from the first to the tenth, the eleventh to the twentieth and 

 the twenty-first to the last day of each month, and the dotted lines 

 represent the average temperature for each month. These months are 

 selected on the supposition that they exert more direct influence than 

 any other time. It will be observed that in a general way the lower 

 the average temperature during these months the following season is 

 correspondingly late. Beyond this it is impossible to go with present 

 data. Other things being constant it would seem that each plant re- 

 quired a certain amount of heat to bring it to a certain stage, and by 

 computing the sums of the daily averages from a certain date, the 

 time of flowering, etc., could be determined from weather records. 



