THE GIRTH-INCREASE OF TREES. 115 
(c.) Progress of girth-increase from month to month.— 
Usually there is a progressive rise from the minimum in April to 
a maximum either in June or July, from which the fall to Sep- 
tember is also progressive. Sometimes the actual minimum is 
in September instead of April. The only exception to this pro- 
gressive rise and fall is in Quercus conferta, in which the percentages 
for April and May are equal, and the observation is quite reli- 
able, as the amounts are substantial and consistent throughout. — 
Of course it results from what has gone before that the rise and 
fall are quicker or more abrupt in some species than in others. 
(d.) Highest and lowest average percentages in each 
month, and the species to which they were due.—The highest 
for April was 9 per cent. of the annual increase in Quercus 
conferta; for May, 22°5 in Fraxinus ; June, 42 in Acer; July, 36 
in Populus; August, 285 in Populus ; September, 9°5 in 
Crategus. The lowest for April was oo in Acer ; for May,9 
or 9'5 in Quercus conferta, Populus, and Crataegus ; June, 23°5 in 
Populus ; July, 25 or 25°5 in Fraxinus, Betula, and Crategus ; 
August, 7 in Fraxinus ; September, 0’5 in Fraxinus. 
2. Species in which the results for 1892-95 are at variance with 
those for 1887-91, or which are otherwise untrustworthy. 
The reasons for regarding as more or less questionable the 
results in this class have been already given in the history of the 
five species which it includes, and need not be repeated. 
(a.) Comparative tendencies towards early or late increase 
in girth —Taking the results for what they are worth, the first five 
species in the Table seem to have a decided preference for the 
last half of the season, while the sixth is in favour of the first half. 
Ist Half 2nd Ha’ 
Apr. | May. | June. July. | Aug. | Sept. | go.5on. | Season. 
ae Sat Reed nae nee ee 
Quercus robur, ... 15 | 15°5 | 175 | 40 21 4:5 | 34°5 65°5 
Carpinus Betulus, o |e |g las lee i tt ee 
Pyrts Anup, SE 86 | BS | ee 57 
Alnus glutinosa, ... e 1io5 | 82] 928 [20 | Pop M5 | 585 
Cytisus Laburnum, 5 114 197 | 285 | 205) 5 | 46 54 
Tilia europoea, ... 1 ha aoe eed © 7 8 oe | 5 | 
