Studies on the Systematics of the Tribe Polygonateae in Liliaceae (s. l.)

黄精族隶属于广义的百合科，通过对其研究历史的回顾，指出了它目前存在的问题，即(1)族的概念和范围不清、(2)属间的界限模糊、(3)族内各属的系统排列不明确．针对这些问题，本文从形态、解剖、胚胎、孢粉和细胞方面对族内各类群进行了野外调查和一些实验工作，本此基础上，并结合前人的工作，对黄精族的系统发育进行了探讨． 一, 形态本文通过黄精族各属大量标本，尤其是国产类群标本的认真研究，并结合6个多月的野外调查资料，分析了本族植物21个形态性状及其状态在属间和属内的分布，指出了一些性状的稳定性及其系统学价值， 二，解剖本文对黄精族5属17个种的茎、根状茎及子房进行了解剖学观察，同时对7属41种植物的叶表皮进行光镜观察，并对5属12种的叶表皮进行扫描电镜的观察，结果表明：(1)七筋姑属花葶的维管柱缺乏纤维鞘，这和本族其它类群不同．(2)扭柄花属、黄精属、竹根七属和鹿药属植物子房中具草酸盐针晶，而七筋姑属和万寿草属未发现这种晶体．(3)本族植物的气孔器均为无规则型，但邻近细胞及其周壁的形状在不同类群中是不同的，据此我们将本族叶表皮划分为七个类型，并认为叶表皮邻近细胞呈多边形、周壁直是黄精族叶表皮最基本的形式． 三，胚胎本文对黄精族3属4种植物以及铃兰(Convallaria majalis)进行了胚胎学研究，其中小玉竹(Polygonatum humile)和铃兰得到了完整的胚胎学资料，实验结果显示(1)黄精族植物小孢子发生过程中胞质分裂均为连续型，胚乳发育为核型；(2)小玉竹的胚囊发育方式为葱型，鹿药(Smilacina japonica)为英地百合型．万寿竹(Disporum cantoniense)和长蕊万寿竹(D. bodinicri)为蓼型，铃兰为葱型或英地百合型；(3)周缘细胞的有或无在小玉竹，鹿药和铃兰中是不稳定的． 四，孢粉本文对6属42种植物花粉进行了扫描电镜观察，结果表明(1)萌发孔的类型和数目在本族中不稳定，系统价值不大；(2)花粉外壁纹饰比较稳定，是一个十分重要的分类学性状．我们将黄精族植物的花粉外壁纹饰划分为9种类型．并认为孔穴型是一种原始类型，其它类型是由它演化而成， 五，细胞在前人工作的基础上，通过与其它性状的综合分析，本文认为黄精族植物有五种原始染色体基数：七筋姑属x=7；万寿竹属和扭柄花属x=8；黄精属x＝9：鹿药属和舞鹤草属x＝ 18;竹根七属x=20． 在上述实验结果的基础上，结合前人的工作，对黄精族的各种性状进行了分析，本文得出如下结论： 1．包括万寿竹属、扭柄花属、七筋姑属、黄精属、竹根七属、鹿药属和舞鹤草属的黄精族是一个单系类群． 2．本文赞同Dahlgren et al．(1985)，Tahktajan (1987)对黄精族系统位置的处理，即它与铃兰族，蜘蛛抱蛋族和沿阶草族关系较近，且共同组成铃兰科．相比之下，黄精族是该科中比较原始的一个族. 3．本文在性状分析的基础上，总结出20个比较稳定、系统价值较大的性状，并指出了它们的演化趋势；同时总结出黄精族原始类群应具有如下特征：(1).具细线形根状茎；(2).地上茎具分枝；(3).叶茎生；(4).具腋生的圆锥或总状花序；(5).花为三基数，花被片离生；(6).花被片具多条开放型脉；(7) .胚珠多数；(8).胚囊发育为单孢子型；(9).厚珠心胚珠；(10) .花粉外壁具覆盖层． 4．本文认为黄精族植物可分为三支：一是以染色体基数x＝9及其衍生的类群，包括黄精属，竹根七属、鹿药属和舞鹤草属；二是以x=8为基数的一支，它包括万寿竹属和扭柄花属；三是七筋姑属单独形成的一支，它的染色体基数x＝7．同时认为万寿竹属是本族比较原始的一个类群． 5．本文认为东亚北方是黄精族植物起源地． 6．本文赞同汤彦承(1978．见汪发缵、唐进1978)对卵叶扭柄花(Streptopus ovalis (Ohwi) Wang et Y.C．Tang)的分类学处理，而不赞同汪发缵、唐进(1983)把金佛山鹿药(Smilacina jinfoshanica Wang et Tang)从鹿药属转隶至黄精属的观点． 7．本文认为鹿药属和舞鹤草属亲缘关系较近，但区别特征明显，从而不赞同LaFrankie (1986),李恒(1990)将二者合并的观点

A New Numerical Method for DEM-Block and Particle Model

As pointed out in Jing and Hudson’s 2002 review paper on numerical methods in rock mechanics, the distinct element method (DEM) is one of the important numerical methods for simulating the mechanical properties of rock masses. Many researchers have paid attention to block deformation and failure in DEM. The updated DEM can be classified into two types: one is the particle model; and the other is the block model. This paper describes the development of a new numerical model, the block and particle model (BPM), to simulate both continuous and discontinuous deformations of rock masses. Both elastic deformation and failure of blocks can be described in this model. The model assumes that a rock mass consists of blocks and each block is formed by particles arranged in a specific way (see Fig. 1), thus formulating a combination of a block model and a particle model. In this model, blocks and particles are connected by springs. Between blocks, there are three springs for adjacent particles: one is a uniaxial spring and the other two are transverse springs. One block has 25 particles. One of the particles is in the center of the cube and the other 24 particles lie in the midpoint between the face center and the four corner points. Spring groups connect these particles. This paper also describes the development of the forces in a block and between blocks and their spring stiffness. The rigidity coefficient of springs between blocks generates the mechanical characteristics of joints in the rock mass. They can be obtained by material tests or wave methods by means of the Goodman model. The rigidity coefficient of springs between particles depends on the characteristics of deformation and failure of a block. The block is cubic and uniform deformation is studied in this model. We assume that the displacement of each particle in a cube block is equal to the displacement of the same position point of the elastic block under the same and known loading; thus, nine equilibrium equations are obtained for each particle. Solving these equations, nine rigidity coefficients can be determined. These coefficients are the function for elastic modulus and Poisson’s ratio. Furthermore, a new failure criterion is suggested for the block failure. This model is verified by an example of rock masses under uniaxial loading. It is shown that numerical results agree well with theoretical ones and laboratory tests, not only for the deformation process but also for the failure process