THE GIRTH-INCREASE OF TREES. 189 
AVERAGE MONTHLY PERCENTAGE IN THE YOUNGER 
CONIFER, 1887-91, COMPARED WITH THE OLDER GROUP. 
| April. | May. | June. | July. | Aug. Sept. 
: | 
| 
Younger Group <---> ~ 5°5 28 26°5 | 185 145 | 7 
Oliar Grills Se | 36 | 18 | 2 
Compared with the older group there is a considerable differ- 
ence in regard to the first and last months, the older group 
having a larger proportion in the first and a much smaller pro- 
portion in the last than the younger trees. But the difference is 
perhaps not greater than might be expected between two groups 
of different ages, to some extent of different species, and under 
observation at different periods, and difference almost disappears 
if we take the first and last two months together. In the older 
group the distribution is somewhat more equable and the 
Maximum is attained later than in the younger trees. 
I. Proportional pine of the first and second half- 
asons of growth. 
The following Table shows that on comparing the two groups 
in this respect, the few species that occur in both have tolerably 
analogous results. 
YOUNGER GROUP. OLDER GROUP, 
Halt, | Half Halt, | Halt 
Araucaria imbricata (2) | 75 25 | Araucaria imbricata (3)- | 73 | 27 
Cupressus Lawsoniana (2) | 73 27 Seqnoia gigantea (4) - 66 34 
Pinus austriaca (1) - 1715 | 28 Pinus austriaca (1) - 64 36 
Retinospora obtusa (1)- | 70°5 | 29 | Cupressus Lawsoniana (1)| 63 | 87 
Thuja gigantea (1) - | 67°5 | 82 | AbiesLowiana(1) - | 56 | 44 
Pinus Pinaster (1) a1 26-1 37 Cedrus africana (1) - 48 52 
» excelsa (3) - ~ | BBS | 44 Taxus baccata (4) - « 45 55 
»» Murrayana q) - $55°5 | 44 | Cedrus Deodara(4) - {| 34 | 66 
Abies Douglasii (3) ~ | 64 46 
»» Hookeriana (1) ~ | 51 49 
» DLowiana(2)- - | 47 53 
» @randis(1)- ~~ | 33 67 
