108 



THE wiiiTi-; imnl;. 



*a7 <a5J' fft? (^ff /^?<P Xr^ /■'^ /S^ /d"^ ^iP^ ^<?^ 



FlQ. 30. — Diagram !?liowing average progress of diaiuefer L'rnwtli (Iirpnwt lii;:Ii) of domiDant trepfl. 



20 40 60 80 100 120 140 ISO 130 200 220 2^ 



ftDE OF DISK 



Fm. 31.— Dlaprnni Bhnwing iliam.t<r (;r..wTli ol ilniiiTnant Ire.v) at varimn In i^lits fn.in (■r..imil (average throiigliout range). 



