THE PHYSIOLOGICAL BASIS OF MORPHOLOGICAL POLARITY IN REGENERATION. II

1. The experiments show that the mass of air roots formed in a stem increases with the mass of the leaf attached to the stem, though it has not been possible to establish an exact mathematical relation between the two masses, owing to unavoidable sources of error. 2. Darkened leaves do not increase the mass of roots formed. 3. In stems suspended horizontally air roots appear on the lower side of the stem, with the exception of the cut end where they usually appear around the whole circumference of the stem. When the lower half of a stem suspended horizontally is cut off, roots are formed on the upper side. It is shown by experiments on leaves suspended horizontally that the more rapidly growing roots and shoots on the lower side inhibit the root and shoot formation in the upper half of such a leaf; and likewise the more rapid formation of roots on the lower side of a horizontally suspended stem seems to account for the inhibition of root formation on the upper side of such a stem. Likewise the more rapid growth of shoots on the upper side of a stem suspended horizontally is likely to inhibit the growth of shoots on the lower side. 4. Each leaf contains in its axil a preformed bud capable of giving rise to a root, which never grows out in the normal stem on account of the inhibitory influence of the normal roots at the base of the plant. These dormant root buds are situated above (apically from) the dormant shoot bud. The apical root buds can be caused to develop into air roots when a piece of stem is cut out from a plant from which the leaves except those in the basal node of the piece are removed. The larger these basal leaves the better the experiments succeed. 5. These apical air roots grow out in a few days, while the roots at the basal end of the stem (which in our experiments dip into water) grow out about a week later. As soon as the basal roots grow out in water they cause the air roots in the more apical region of the stem to dry out and to disappear. 6. In addition to the basal roots, basal nodes have also an inhibitory effect on the growth of the dormant root buds in the apical region of a stem. This is indicated by the fact that a stem with one pair of leaves near the base will form apical air roots more readily when no node is situated on the stem basally from the leaf than if there is a node basally from the leaf.     

中国似鮈属鱼类的形态变异及地理分化研究

对似鮈属鱼类进行了形态测量和主成分分析。结果表明区别似鮈和桂林似鮈的重要特征胸鳍末端是否超过腹鳍起点与尾柄高同尾柄长的比例相互之间有一定的相关性,但是在研究的样本中没有截然的界限,而是有较大的重叠,难以区分。其他的特征则没有相关性。从地理分布看,同一地点的样本在上述特征上有一定的区别,但是没有发现明显的南北或东西地理变化的规律。因此似鮈属鱼类应该只划分为一个种,桂林似鮈为似鮈的同物异名。     

鹅观草属三个种的形态变异与核型的研究

本文通过对鹅观草属的三个种:鹅观草(Roegneria kamoji Ohwi)、纤毛鹅观草(R. ciliars (Trin.) Nevski)和竖立鹅观草(R. japonensis(Honda)Keng)的形态学比较和核型分析研究了该三个种的系统关系。R. kamoji与R. ciliaris、R. japonensis形态上的差异明显,而后二个种差异甚小,难以进行划分。R. kamoji的核型公式为:2n=6x=42=30m+8sm+4SAT;R. ciliaris为:2n=4x=28=18m+6sm+4SAT;R. japonensis为:2n=4x=28=18m+6sm+4SAT。t-测验的结果表明R. ciliaris与R. japonensis的核型无显著差异。因此笔者认为R. ciliaris和R. japonensis应合并为一种系内的分类群。     

VARIATIONS IN THE PHYSIOLOGICAL STATE OF THE COMMON COCKLE (CERASTODERMA EDULE (L.)) IN THE LABORATORY AND IN SOUTHAMPTON WATER

Various physiological indices (i.e. body condition index, scopefor growth and net growth efficiency) have been used to examinethe metabolic state of the common cockle (Cerastoderma eduleL.) at different sites in Southampton Water, U.K. The resultsshow that there is a measurable difference in the conditionindex of cockles collected from different localities. Thesedifferences can be broadly related to the level of contaminationof the site with metals and hydrocarbons. All the indices suggestthat cockles inhabiting the eastern, less polluted side of SouthamptonWater are in a better metabolic state than in those from somesites on the western side close to industrial areas. Growthand longevity also appear to be site related. (Received 25 September 1989; accepted 25 March 1990)     

INTRAPLANT MORPHOLOGICAL VARIATIONS IN GRASSES

Clonal progenies were developed from individual nodal segments of bromegrass, cormlets of timothy, and secondary basal buds of sorghum. The parent plants were morphologically unstable or chimeral and occurred in either hybrid or inbred populations. Intraplant clonal progenies usually continued to be unstable through the second clonal generation. Marked deviating types occurred within clonal rows. Intraplant comparisons were made of inflorescence characters and seed-set following open-pollination of unstable plants from inbred lines of smooth bromegrass. Significant differences occurred between characters in panicles from different parts of the same plant.     

SOME MORPHOLOGICAL VARIATIONS IN THE DIATOM CYMBELLA CISTULA1,2

Several populations of Cymbella cistula (Ehr.) Kirchn. were studied. An epiphytic population contained smaller specimens than any reported by recent authors. The size range of members of the epiphytic population included specimens as small as 24 μ long by 11 μ wide. These small specimens could be mistaken for C. cistula var. maculata (Kütz.) V. H., but differ in having isolated puncta, which, may be indistinct, and somewhat coarser striae.     

中华鮡与前臀鮡的形态差异和物种有效性

采用主成分分析方法研究中华与前臀物种的有效性问题,并利用主成分分析结果中起主要作用的性状作差异性的统计分析,为分类性状的相关性提供了数学依据。结果表明:1)中华与前臀的主要鉴别特征在于前者之臀鳍起点至尾鳍基的距离小于至腹鳍起点的距离,后者反之;2)前者尾柄高大于前鼻孔至眼前缘距离后者反之;3)前者脂鳍基末端至尾鳍背侧起点的距离小于尾柄高,后者反之。据主成分分析及显著性t值检验结果。笔者观点与原文献作者观点完全一致,中华与前臀应是两个不同独立种。两物种形态上的差异主要表现在与游泳等行为有关的性状特征上,而且也是对不同小生境长期适应的结果。     

中华与前臀的形态差异和物种有效性

采用主成分分析方法研究中华（鱼兆）与前臀（鱼兆）物种的有效性问题,并利用主成分分析结果中起主要作用的性状作差异性的统计分析,为分类性状的相关性提供了数学依据.结果表明：1）中华跳与前臀（鱼兆）的主要鉴别特征在于前者之臀鳍起点至尾鳍基的距离小于至腹鳍起点的距离,后者反之;2）前者尾柄高大于前鼻孔至眼前缘距离后者反之;3）前者脂鳍基末端至尾鳍背侧起点的距离小于尾柄高,后者反之.据主成分分析及显著性t值检验结果.笔者观点与原文献作者观点完全一致,中华（鱼兆）与前臀铫应是两个不同独立种.两物种形态上的差异主要表现在与游泳等行为有关的性状特征上,而且也是对不同小生境长期适应的结果.     

中华(鱼兆)与前臀(鱼兆)的形态差异和物种有效性

采用主成分分析方法研究中华(鱼兆)与前臀(鱼兆)物种的有效性问题,并利用主成分分析结果中起主要作用的性状作差异性的统计分析,为分类性状的相关性提供了数学依据.结果表明:1)中华跳与前臀(鱼兆)的主要鉴别特征在于前者之臀鳍起点至尾鳍基的距离小于至腹鳍起点的距离,后者反之;2)前者尾柄高大于前鼻孔至眼前缘距离后者反之;3)前者脂鳍基末端至尾鳍背侧起点的距离小于尾柄高,后者反之.据主成分分析及显著性t值检验结果.笔者观点与原文献作者观点完全一致,中华(鱼兆)与前臀铫应是两个不同独立种.两物种形态上的差异主要表现在与游泳等行为有关的性状特征上,而且也是对不同小生境长期适应的结果.