272 IOWA ACADEMY OF SCIENCE Vol. XXV, 1918 



sod established. Tlie grass is mowed and allowed to remain on 

 the soil as a mulch. The trees in this plot from which the buds 

 were studied are located on a southwest slope. 



Plot Five (cover crop) receives same treatment as i)lot two. 

 It has a southwest slope. 



Plot Six (ck)ver sod) receives the same treatment as plot one. 



This work was a continuation of tlie l)ud study inaugurated 

 by F. ]\r. Harrington. The same trees which he had selected 

 were chosen with the idea that his work could be used as a check 

 on our results. These trees, consisting of one tree of the Jona- 

 than and one of the Grimes Golden from each of the six plots, 

 were carefully selected as representing the average gTOwth and 

 [iroduction of the trees of the respective plots. 



\n order to eliminate as much error as possible, due to a lack 

 of uniformity in buds, all buds were collected from old spurs 

 which bore no flowers in the spring of the current year. Also 

 since the flowers of a cluster differ in development according to 

 position in the cluster, only the terminal flower of the cluster 

 was used in making comparisons. 



Despite these precautions there still re;nains nuich chane^^ fi)r 

 error. Buds on different spurs vary in time of formation and 

 in rate of development. Hence the buds studied at successive 

 collections, unless a large number of l)uds are included, vary so 

 much in the proportion of backward and forward buds, th^it 

 their average time of formation and rate of development may 

 be far fi-om the average of all the buds of a tree. Then there 

 are a number of factors other than soil conditions, such as the 

 health of trees, exhaustion from previously bearing a heavy crop, 

 and individual characteristics that cause variation and make 

 it impossible to draw conclusions except from a large amount 

 of data; 



At each collection ten buds were chosen from each of the 

 twelve trees. The first collection was made on July 6, 1916, and 

 during the following forty-two weeks, nineteen similar collec- 

 tions were made at intervals of approximately two weeks during 

 active growth of summer, fall, and spring and at intervals of 

 two to four weeks during winter when growth was inactive. 



As soon as the buds were removed from the trees they w^ere 

 placed in labeled vials and immediately sent to the laborator^' 

 where all of the cutinized scales were removed, leaving only the 

 vital parts of the ])ud and a very short peduncle to be killed. 



