1917] MOORE—CONIFEROUS FORESTS 157 
often so dry that neither reproduction nor herbaceous vege- 
tation can become established, no matter how much light it 
receives. 
Counts of the reproduction of spruce, fir, white pine, and cedar, 
correlated with age, showed that spruce, fir, and white pine become 
established only at intervals of several years, while cedar comes in 
every year. The cause of the failure of spruce and fir to become 
established every year is apparently not related directly to climatic 
factors, because the season of 1916 was unusually moist and favor- 
able, yet practically no seedlings of these 2 species could be found. 
Probably the reason for this periodicity in spruce and fir reproduc- 
tion is to be sought largely in the seed supply. White pine repro- 
duced abundantly in 1916, so that climate can be eliminated as a_ 
factor; but since it is equally impossible to eliminate the matter 
of seed production, the periodicity of white pine reproduction may 
be due to both the season and the seed supply. 
In fir there are indications of a periodicity of reproduction 
which is of Poneuieranty more suse ehoorenio | en that due » the 
seed supply. 1 about 
middle age, the fir reereduction is ‘nearly all composed. of large : a 
seedlings approximately 1-3 ft. in height; young seedlings are 
Scarce. In these cases it appears that the fir came in profusely a : : 
— a set of savisenies conditions different from the present oe 
Just what these conditions were it is impos: : 
out ie fester shy One of them may have been stronger light than 
at present. Indications of this were found in. the fact that some _ 
_ Of these cases of fir reproduction occur in stands which were for- 
_merly more open than they now are; also, small fir repr duction 
is abundant in young stands with a full but not very heavy canopy. 
= sion @. _ Another factor may b be d 2s lecré 
ible to pos tea - = 
