1888-89.] Annital Increase in Girth of Trees. 395 



As it happened that the second, third, and fourth years 

 of the decennial period were seasons of unusual severity, 

 it would not be safe to conclude that the results obtained 

 represent the usual average of variation in the annual girth- 

 increase. At the same time, in other years great variations 

 occurred in not a few trees which had either escaped the 

 effects of the three consecutive bad seasons, or had entirely 

 recovered from them. 



Thus, taking only trees which always preserved a healthy 

 appearance, the following variations, quite independent of the 

 three severe seasons, may be quoted : — 



Beech, 0-65 aud 0'25 Sequoia, 1*80 and 0"95 



Ornus, 0-50 „ 0-20 Deodar, 1-20 „ 0-45 



Sycamore, 0-55 „ 0*20 Yew, 0-65 „ 0-20 



Oak, 0-95 „ 0-50 Evgn. Oak, 0-55 „ 0-25 



From these facts it follows that the average rate of sjrowth 

 in trees cannot be ascertained even approximately by a single 

 year's measurement, or with any great accuracy unless by 

 several years' measurements. 



4. Annual Range in the Aggregate G-irth- Increase. 



The aggregate range is naturally not so great as the indi- 

 vidual range, as the maxima and minima of the separate 

 trees are not concentrated on two or three particular seasons, 

 but are distributed throughout the decennial period, so as 

 partially to counteract each other when taken in the aggre- 

 gate. Still the aggregate results are remarkable enough. 

 In the deciduous class, comprising 28 trees, the maximum 

 was nearly double the minimum, the figures being 19 "35 

 inches and 1015 inches. In the evergreens, comprising 19 

 trees, the difference was not quite so great, the maximum 

 being 16"60 and the minunum 9"60. As in this comparison 

 the species in which several trees were tested exercise a 

 preponderating influence over those in which only one tree 

 was tested, I have reduced them all to a common value by 

 taking the average amounts for the sjyecies instead of the 

 amounts for the individual trees. This proceeding, how- 

 ever, does not materially modify the results. 



