280 IOWA ACADEMY OF SCIENCE Vol. XXV. 191 S 



Plot I. According to the measurements the flower buds were 

 slightly more advanced on blue grass sod than on other plots 

 excepting- Plot 1 of clover sod. 



In Table II, the relative development of the flower l)uds of 

 the Jonathans from December 9 to April 10 of 1917, is shown 

 by the relative leng1:hs of the carpels of the terminal flowers. 

 When the different plots are compared as to the shortest and 

 longest carpels recorded on the different dates, it will be noted 

 that with two exceptions this table is in accord with what is 

 shown in Table I in reference to the relative development of buds 

 on the different plots. The exceptions referred to occurred on 

 April 10 on plat 5 cover crop, and plot 3 clean tillage. The bud 

 containing a flower with some stamens in synapsis and recorded 

 under clean tillage was an exceptional bud, for the IhuI least 

 advanced was less developed than the buds least advanced on 

 the other plots and the boids on the average were less developed 

 than the buds on the other plots. But on plot 5 cover crop the 

 buds collected on April 10 were on the average more developed 

 than buds collected from other plots. Either the buds on tliis 

 plot developed more rapidly than buds on other plots, during 

 , the latter part of March and early part of April, or the buds 

 of this collection happened to be exceptional. Unfortunately no 

 flower buds, which would have sers^ed as a check on plot 5, 

 were found in the collection from plot 2, cover crop, on April 

 10. The dates of blooming were practically the same on all 

 plots. The cool spring which retarded blooming and thereby 

 afforded an opportunity for the flowers least advanced to catch 

 up may acco'unt for this. It may be that there is a difference 

 in the rate of development just preceding the blooming period 

 due to different methods of soil management, and it is a'so pos- 

 sible that buds backward in development surpass other buds in 

 rate of development just preceding the blooming period. From 

 the two tables it is seen that the flower buds of the Jonathan 

 developed most rapidly from the time of their fonnation to 

 November, and from February till time of blooming. During the 

 remainder of the season development was slow. 



In tables III and IV are given the measurements of the least 

 and most advanced buds of the Grimes Golden on the different 

 plots. The trees of the Grimes Golden formed fewer flower 

 buds than the Jonathan on the ]ilots where there was cultiva- 

 tion and the measurements are less complete. The tree on plot 



