1909.] 



PUBLIC DOCUMExNT — No. 31. 



177 



easily demonstrated to the naked eye, canncjt be so easily meas- 

 ured and recorded statistically. There is also a remarkable 

 difference in the marginal serrations in leaves from trees on 

 diiferent stocks. Tracings of ty])ical leaf margins are compared 

 in Fig. 2. JW measuring tlui length of a large number of leaf 



serrations in each lot, averages have been secured which will 

 serve for numerical com])arison. In order to secure these meas- 

 urements with reasonable accuracy the leaf margins were con- 

 siderably magnified. On this account the units used in the 

 following comparison are arbitrary and need not be regarded. 

 (They were approximately one-eightieth of an inch.) 



Comparison of Marginal Serrations. 



Average. 



Standard 

 DeTiation. 



On Americana, 

 On Wayland, 

 On Marianna, 

 On peach, . 



38.00 

 3.'). 08 

 31.02 

 34.75 



9.32 

 8.H 

 5.39 

 6.65 



