70 THE THIRD YEARBOOK 



lated would be 1,907,400 square miles; i. e., equal to about thirty- 

 four times the area of Illinois. 



The fifth year the number of seeds would be sufficient to furnish 

 plants as thickly as those found on the quarter of an acre for an 

 area equal to sixteen times that of the entire earth. 



These measurements and calculations give (a) an idea of the 

 vitality and the tremendous push and rush of the living things ; (h) 

 since there is no such increase, as an actual fact, they indicate the 

 degree of failure on the part of the plant to get its seeds properly 

 scattered and safely planted, and also the enormous resistance 

 offered by other plants and climatic agencies to the growth and 

 spread of the verbena. 



II. SEASONAL CONDITIONS : WERE THEY FAVORABLE OR 

 UNFAVORABLE? 



1. Rainfall. — One inch of rainfall furnishes 540 fifty-gallon 

 barrels of water per acre, or 135 barrels for the quarter acre. Dur- 

 ing the month of May, June, July, August, and September, w^here 

 the verbenas grew, the rainfall due the plants, according to the 

 thirty-year average given by the Weather Bureau, is 16. i inches, 

 or 2,229 barrels. The actual rainfall for three months in 1901 

 was 13.9 inches, or 1,874 barrels. There was, therefore, a shortage 

 of 2.6 inches, or 351 barrels. That is, from this cause alone the 

 vitality of the plants was reduced by about 16 per cent. This may 

 be viewed in different ways : (a) that only about eight plants out 

 of ten would grow this season ; or (h) that eight seeds out of ten 

 would mature ; or (c) that the general vitality was lowered, which 

 would be felt the following season. 



2. Sunshine. — The Weather Bureau records for the past eight 

 years show that this region has received 65 per cent, of the sun- 

 shine possible during the months under consideration. In the year 

 1 901 this area received 68 per cent, of the possible sunshine. It 

 follows therefore that, since plants are most active in sunshine, 

 there was an overstimulation of 3 per cent, above the normal. 

 Since, also, during sunshine plants are most active in the trans- 

 piration of water, and since there was a shortage in the supply of 

 16 per cent., it follows that the combination of these two causes 

 operated to intensify the strain upon the plant. The plant endeavors 



