58 



a faithful observance of the .practice recommended by the Bureau of 

 Entomolog}^ The menace from this source is certainly sufficient to 

 justify the adoption of strong measures tending to largely reduce, if 

 not to prevent altogether, the growth of seppa cotton. The recom- 

 mendation made by Prof. E. D. Sanderson, while State entomologist 

 of Texas, that laws be passed making it a punishable offense to allow 

 the unchecked growth of seppa cotton, seems to the writers fuUj^ justi- 

 fiable and commendable. 



INCREASE IN LEAF ABEA OF COTTON. 



The advisability of making observations upon this point was sug- 

 gested by the attempts made to poison hibernated weevils by spraying 

 early cotton with an arsenical insecticide. As the weevils fed so 

 exclusively in the most recently unfolded growing portions at the tips 

 of the stems, it was evident that the rapidity of increase in the leaf 

 area would at least indicate the frequency with which spraying would 

 have to be repeated in order to keep in a poisoned condition the very 

 limited portion upon which the weevils fed. 



Although the observations were made after midsummer, the plants 

 used were of the right size to indicate the points desired. Two series, 

 each including five average plants, were selected. 



The plants used in Series 1 had 8 leaves at the time of the first 

 observation. Those used in Series II were older and averaged about 

 30 leaves each. The leaves borne upon the main stem were classed 

 as primary and those from side branches as secondary leaves. Upon 

 the date of each of the 5 observations made, the number of leaves in 

 each class was ascertained, an average leaf in each class was quite 

 accurately measured, and the total product of numbers and area thus 

 found was considered as the approximate leaf area of the plant. The 

 error has been reduced as much as possible by taking an average of 

 the 5 plants in each series as representing a typical plant, and it is 

 with these results that comparisons have been made. 



Table XI. — Estimated increase in leaf area of cotton, averages of five plants. 



Date of examination. 



1902. 



Series I: 



August 30 



September 13. 



September 25. 



October 6 



October 17 



Series II: 



August 30 



September 13. 



September 25. 



October 6 



October 17.... 



Primary leaves. 



Average 



number 



per 



plant. 



8.0 



8.6 



9.8 



11.0 



13.2 



7.8 

 8.4 

 9.8 

 9.6 

 10.0 



Average 

 area , 

 plant. 



Sq. in. 

 64.0 

 136.8 

 231.6 

 309.6 

 376.6 



177.2 

 229.2 

 211.0 

 214.8 

 216.8 



Percent- 

 age of 



daily in- 

 crease. 



8.0 

 5.4 

 3.0 

 2.0 



2.0 

 .04 

 -1.0 



Secondary leaves. 



Average 

 number 



per 

 plant. 



0.0 



8.0 



16.6 



22.6 



31.0 



21.6 

 24.8 

 42.4 

 52.6 

 67.4 



Average 

 area, 

 plant. 



Sq. in. 



41.2 

 187.4 

 347.8 

 522.4 



266.8 

 341.4 

 514. 

 619.2 



Percent- 

 age of 



daily in- 

 crease. 



30.0 

 7.8 

 4.6 



2.0 

 3.6 

 1.8 

 2.1 



a Decrease of 1 per cent due to falling of old primary leaves. 



