. Bulletin of the Department of Agriculture. Agriculture; Agriculture. LABCH MISTLETOE. positively phototropic. The possible influence of the low absolute humidity and rapid evaporation on the entrance of host, reproduc- tion, etc., is counteracted by the parasite by means of special struc- tures enabling it to withstand long periods of drought. Probably no factor of the region so greatly aids the destructive effects of the mistletoe on the larch as the high, strong winds so prevalent in these mountains. The velocity of the winds is sometimes very great. During 1913 hundreds of reserved y
. Bulletin of the Department of Agriculture. Agriculture; Agriculture. LABCH MISTLETOE. positively phototropic. The possible influence of the low absolute humidity and rapid evaporation on the entrance of host, reproduc- tion, etc., is counteracted by the parasite by means of special struc- tures enabling it to withstand long periods of drought. Probably no factor of the region so greatly aids the destructive effects of the mistletoe on the larch as the high, strong winds so prevalent in these mountains. The velocity of the winds is sometimes very great. During 1913 hundreds of reserved yellow pines on the sales area of the "Whitman National Forest were up- rooted. The wind in this case was mate- rially aided by the insecure rooting of the trees on the surface of a hard stratum of rocks and gravel, together with a cer- tain amount of decay in the brace roots. This is a condition often found in cases of this kind. Strong winds probably do greater injury to the larch than to any other conifer. An examination of the branching or crown of a mature or middle-aged healthy larch will show that in most cases, especially in windy regions, the tree has been able to reach the standard size only through the production of several generations of branches replacing those broken off by the wind and }>y other causes (fig. 2). The loss of branches through crowding or natural priming is not here considered. Trees standing under open conditions from the beginning will show this interesting phenomenon of regeneration. Increasing ;;Lr<\ within a certain limit, on the part of the main trunk docs not interfere with the anatomical and physiological connections ' old branches. Consequently, branches forming at any age sufticientty high on the trunk to escape the influence of suppression should and would remain intact, barring all deteriorating influences, during the natural life of the tree. Tree- with wood exhibiting a natural brittleness, which is always very pronounced
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