河南省白榆良种选育协作组,经六年的多点无性系比较,已筛选出一批生长快、干形直、易繁殖、用途广的白榆优良无性系。为选择育种、推广良种并给木材利用提供科学依据,特作此鉴定性试验。一、试材采集和试验方法 1985年6月21日在孟县林科所(北纬34°28′,东经112°41′,属华北暖温半干旱地区,年均气温13.9℃,年降雨量675.9毫米,绝对最高气温42.8℃,绝对最低气温 Henan white elm breeding cooperation group, after more than six years clonal comparison, has been screened a number of growing fast, stem-shaped straight, easy to breed, wide use of elm elite clones. In order to choose breeding, popularization of seeds and wood to provide a scientific basis, this special test. First, the sample collection and test methods June 21, 1985 in Meng County Linke (34 ° 28 ’north latitude, longitude 112 ° 41’, is a warm and semi-arid northern China, with an average annual temperature of 13.9 ℃, the annual rainfall 675.9 mm, the absolute maximum temperature of 42.8 ℃, the absolute minimum temperature