<正>通过对苏北杨树溃疡病发生状况的调查发现，主要有4种溃疡病症状：水泡型、凹陷小圆斑型、不规则黑斑型、烂皮型。其中以大型不规则黑斑溃疡病危害最重，对各种类型的杨树溃疡病组织进行分离、病原菌接种。结果表明，不同病啄菌对不同场蚓品种的致病力有一之差异。金黄克囊孢（Cytospora chrysosperma）对N1895扬和1-72杨的致病力要大于拟茎点霉（Phomopsis macrospora）和七叶树壳梭孢（Fusicoccum aesculi），而詹两者对NL895和1～72杨的致病力相近，各病原菌对1-69场的致病力相近。

The paraffin cut method was used to observe the flower bud differentiation of Tilia miqueliana. The results showed that Tilia miqueliana hiemal bud belonged to mixed bud. After the sprout of mixed bud, flower bud was formed in leaf axil. Flower bud was differentiated in the same year from the end of March to the early May, i. e., it took about 35 to 40 days totally. The flower bud differentiation was that of short duration and fast development. The differentiation included two processes with inflorescence differentiation and floret differentiation. All flower bud differentiation was divided into seven developmental stages, i. e., initial differentiation phase, inflorescence primordium differentiation phase, floret primordium differentiation phase, sepal primordium differentiation phase, petal primordium differentiation phase, stamen primordimn differentiation phase and pistil primordum differentiation phase.