24 BULLETIN 234, U. S. DEPARTMENT OE AGRICULTURE. 
clean and the remainder left for seed. Even in the seed blocks 
thinnings were made to remove lagging, converter poles, and large 
stull trees, so that the seed groups finally consisted of from 30 to 60 
trees ranging from 7 to 11 inches in diameter. In exposed situations 
over 90 per cent of the trees left have been blown down, and many 
others have died from sun scald or from the drying out of the soil. 
In the more sheltered situations, particularly where the original 
stand had been somewhat open, windfall has been much less. This 
heavy loss from windfall quickly demonstrated the impractibility 
of such a system for general use in lodgepole-pine stands. These cut- 
tings were not a fair test of the wind firmness of the species, however, 
for to reduce the number of trees per acre of any species from 500 
or 1,000 to about 50, particularly when the individual trees were 
tall and slender, could hardly result otherwise than in excessive 
windfall. 
The next change in the marking system naturally aimed to elimi- 
nate windfall. In the spring of 1909 the strip system was applied. 
The timber was clean cut in strips, with seed strips from 100 to 150 
feet wide left absolutely intact between them. The width of the 
clean-cut areas was from one to three times that of the seed strips. 
This system proved successful in reducing windfall to a negligible 
amount, but in other respects had no advantage over the seed-tree 
group system. In both systems the operator gradually accumulated 
a surplus of cordwood and small stulls in excess of the market de- 
mand, while the Government lost from the clean-cut areas many 
small, thrifty trees capable of rapidly developing into large material 
under better management. At the same time there remained in 
the seed strips many large, slowly growing trees wanted by the 
operator and not of use in the stand except to prevent windfall. 
Neither of the systems is satisfactory in regard to watershed pro- 
tection, nor does either tend to increase the volume or better the 
quality of the succeeding stand. 
Another important drawback to the systems mentioned was their 
lack of adaptability to the great variety of conditions found on the 
sale area. Overdense stands of lagging and converter poles, badly 
in need of thinning, remained untouched, because a sufficient amount 
of such material was being obtained from the clear-cut areas. Over- 
dense and moderately dense even-aged stands, uneven-aged stands, 
and old and young stands were all cut in exactly the same Way. 
For this reason the system of cutting was still further modified in the 
fall of 1910 and again slightly modified hi the summer of 1913. The 
present marking rules are as follows: 
