凤丫蕨孢子壁的结构和发育研究

利用光镜、扫描电镜和透射电镜对裸子蕨科（Hemionitidaceae）凤丫蕨（Coniogramme japonica（Thunb.） Diels）孢壁的结构和发育进行了研究。结果表明,凤丫蕨孢子外壁表面光滑,由2层构成,即薄的内层和厚的外层。周壁分为周壁内层和周壁外层两部分,周壁内层中上部具辐射状排列的小柱状成分,周壁外层由鳞片和小球体疏松交织成平面或立体网状,由两层周壁共同构成孢子表面皱状纹饰的轮廓。探讨了凤丫蕨孢子周壁的来源,为孢粉学和蕨类植物系统演化研究提供基础资料。     

水杉花粉外壁超微结构的观察

本文报道水杉（Metasequoia glyptostroboides Hu et Cheng)花粉外壁透射电镜资料,与杉科各属花粉特征做了比较,根据透射电镜观察表明,水杉花粉外壁由外壁外层和外壁内层组成,外壁外层由昆密联结的颗粒层和分布稀少的乌氏体组成,后者表面具小刺及不明显的纵向小沟,外壁内层具有十分清楚的片层状结构,由10－15片组成,全部片层均具三层壁结构,最外面（靠近外层）的几片,三层型结构特别清楚,明晰。有的三层型结构层中间的白线松散,形成三根极细的白线。     

水杉花粉外壁超微结构的观察

本文报道水杉（Metasequoia glyptostroboides Hu et Cheng)花粉外壁透射电镜资料,与杉科各属花粉特征做了比较,根据透射电镜观察表明,水杉花粉外壁由外壁外层和外壁内层组成,外壁外层由昆密联结的颗粒层和分布稀少的乌氏体组成,后者表面具小刺及不明显的纵向小沟,外壁内层具有十分清楚的片层状结构,由10－15片组成,全部片层均具三层壁结构,最外面（靠近外层）的几片,三层型结构特别清楚,明晰。有的三层型结构层中间的白线松散,形成三根极细的白线。     

海金沙孢子壁结构和发育的研究

利用光镜、扫描电镜和透射电镜对海金沙科(Lygodiaceae)海金沙[Lygodium japonicum (Thunb.) Sw.]孢壁的形成和发育进行了研究.结果表明:海金沙孢子壁由内壁、外壁和周壁3部分构成.外壁由2层构成,即薄的内层和厚的外层,其中外层是在四分体分离前通过孢粉素的逐层沉积并浓缩凝聚而形成的均质层,其表面具不明显的疣状突起.周壁由绒毡层残余物在外壁表面逐层沉积形成,可分为周壁内层、周壁中层和周壁外层3部分;周壁中层具辐射状排列的长条形成分,周壁外层形成瘤状纹饰的轮廓.本研究为孢粉学和蕨类植物系统演化分析提供基础资料.     

藏马鸡卵壳的扫描电镜观察

利用扫描电镜对我国特有珍禽──藏马鸡的卵壳进行了超微结构观察。电镜下显示：藏马鸡卵壳从内向外由壳膜层、锥体层、海绵层和表层等组成。壳膜层内层致密、含少量纤维,外层为纵横交错成网状的纤维结构,锥体层由许多乳头状突起密集排列组成,海绵层为似沉积岩层的层状结构,表层在卵壳最外面,上由具保护性的透明蛋白质薄膜覆盖。与同属的褐马鸡的卵壳进行比较,其超微结构存在差异。     

陕南寒武系幸运阶宽川铺组软体动物Mediata鳞片状纹饰显微结构

马哈螺(Maikhanellids)是一类具单壳的、壳体表面发育特殊鳞片状纹饰的软体动物化石。目前对maikhanellids鳞片状纹饰的研究主要涉及整体形态和分类,关于鳞片状纹饰的组成和内部结构的研究为数甚少。马哈螺科中Mediata属以壳顶大(约占整个壳面的1/3–1/2)、不同大小的长卵形鳞片状纹饰、背部具有一条从壳体前端延伸至壳体后端的宽脊、无规则的生长纹等特征有别于该科其他各属。本文基于陕南寒武系幸运阶宽川铺组产出的大量保存精美的Mediata标本,详细描述了Mediata鳞片状纹饰的形态特征、超微结构和原始矿物组成。Mediata的纹饰鳞片从外到内可分为外、中、内三层。外层为覆盖整个鳞片状纹饰的原始角质层。中层由磷灰石集聚体组成,该集聚体在中层外部表现为紧密且无定形排列,说明其原始成分可能为有机质;而在中层内部集聚体则排列成纤维状结构,暗示其原始矿物成分可能为文石。内层由平行于鳞片长轴方向的束状结构组成,束状结构内部有许多相互平行的微米级细长空心棱柱状结构,棱柱状结构之间被有机膜分隔。Mediata内层的超微结构和蒙古西南部纽芬兰统Bayangol组发现的软体动物Posta...     

白头翁属的花粉形态研究

白头翁属(Pulsatilla Mill．)花粉共有4个萌发孔类型：1．三沟类型; 2．散沟类型; 3．散孔类型; 4．二型花粉类型。各类型之间的演化趋势是：三沟→散沟→散孔类型。外 壁表面具大、小两型小刺和小穿孔。根据外壁表面小刺的粗细和小穿孔的分布,可将本属分 为两个类群,即一类为表面呈波浪状,小刺较粗,基部具垫状隆起,小穿孔分布在隆起之间的低 凹处; 另一群外壁表面平,刺较细,排列稀,小穿孔均匀分布在花粉的表面上。利用透射电镜观 察本属三沟型和散孔型的外壁内部结构是一致的,即都由薄的内层与厚的外层组成。内层在 沟和孔下面均加厚,在沟间区和孔间区变薄。外层包括覆盖层、柱状层和基层。     

瓦韦孢子壁的结构和发育的研究

利用光镜、扫描电镜和透射电镜对水龙骨科（Polypodiaceae）瓦韦(Lepisorus thunbergianus (Kaulf.) Ching)孢子壁的结构和发育进行了研究。研究结果表明瓦韦孢子两侧对称、单裂缝,表面具波纹状纹饰。孢壁从内到外由内壁、外壁和周壁三部分构成。外壁来源于绒毡层物质,由外壁内层和外壁外层构成,外壁外层表面的波纹状纹饰形成孢子表面的纹饰轮廓。周壁薄,紧贴外壁表面,由2层片状结构叠合而成。在外壁外层形成过程中,孢子表面和周围出现较多小球。本文探讨了孢壁各层的结构、来源和发育过程,为蕨类植物系统学和孢粉学研究积累资料。     

云南松花粉形态研究

在云南松(Pinus yunnanensis Fr.)小孢子发生发育过程中,花粉母细胞、四分孢子及花粉粒均见有粘连现象。花粉气囊的形态、大小变化复杂多样。除一般具两个正常气囊的花粉粒外,还观察到气囊不发育、具一个气囊、二个异形气囊、三个气囊和四个气囊的花粉粒。成熟花粉壁从外至内可分为外壁外层、外壁内层、内壁外层和内壁内层,它们的构成成分及形态均有明显差别。贮存后花粉的内壁结构发生了明显变化。     

蜈蚣草孢壁发育及其系统学意义

利用光镜、扫描电镜和透射电镜对凤尾蕨科(Pteridaceae)蜈蚣草(Pteris vittata L.)孢壁的形成和发育进行研究。结果表明:蜈蚣草孢子四面体型,极面观钝三角圆形,赤道面观半圆形或超半圆形,近极面具瘤状纹饰和近极脊,远极面具脊并连成网状,具赤道环;孢子具乌毛蕨型外壁,由外壁外层构成纹饰的轮廓;实心型周壁由2层构成,且内层薄、外层具小球体。结合孢子外壁和周壁的发育特征,认为凤尾蕨科与裸子蕨科和水蕨科的亲缘关系较近,支持将裸子蕨科和水蕨科置于凤尾蕨科。     

Fine structure of germinatingPenicillium megasporum conidia

Summary Penicillium megasporum conidia have spore walls consisting of several layers. There is no visible change in the outer wall layers during spore germination, but the inner layers increases in thickness on only one side of the spore, resulting in a rupture of the outer wall layers and subsequently in germ tube formation. Invaginations in the plasma membrane disappear as the germ tube forms and emerges, and the nucleus migrates into the developing germ tube. Mitochondria gather at the base of the germ tube during its formation. During germination, the amount of lipid in the spore decreases and portions migrate into the germ tube. Membrane-bound, electron dense bodies are present in resting spores. These bodies decrease in size as germination proceeds, and the cytoplasm in the developing germ tube appears much more electron dense than the cytoplasm within the spore.     

Relationship between microtubule orientation and patterns of cell expansion in developing cortical cells of Lemna minor roots

In actively growing cortical cells in the elongation zone of Lemna minor L. roots, both longitudinal (radial and tangential) and transverse walls expand in both length and width. The longitudinal walls of the three types of cortical cells in the root (i.e. outer, middle and inner) showed the largest expansion in the longitudinal axis. In contrast, the inner cortical cells exhibited the least expansion in width, whereas the middle cortical cells displayed the largest expansion in width. Thus, the profiles of the expansion of longitudinal walls were characteristic for the three types of cortical cells. In this study, both the orientation of cortical microtubule (MT) arrays and their dynamic reorientation, and the density of cortical MTs, were documented and correlated to the patterns of cell wall expansion. Significantly, transverse arrays of cortical MTs were most prominent in the radial walls of the inner cortical cells, and least so in those of the middle cortical cells. Toward the base of roots, beyond the elongation zone, the orientation of cortical MTs shifted continuously from transverse to oblique and then to longitudinal. In this case, the rate of shift in the orientation of cortical MTs along the root axis was appreciably faster in the middle cortical cells than in the other two types of cortical cells. Interestingly, the continuous change in cortical MT orientation was not confirmed in the transverse walls which showed much smaller two-dimensional expansion than the radial walls. Additionally, the presence of fragmented or shortened cortical MTs rapidly increased concomitantly with the decrease of transversely oriented cortical MTs. This relationship was especially prominent in the transverse walls of the inner cortical cells, which displayed the least expansion among the three types of cortical cells investigated. In the root elongation zone, the density of cortical MTs in the inner cortical cells was about three times higher than that in the other two cortical cell types. These results indicate that in the early stage of cell expansion, the orientation of cortical MTs determines a preferential direction of cell expansion and both the shifting orientation and density of cortical MTs affect the magnitude of expansion in width of the cell wall.     

SCHIZOGENY AND ULTRASTRUCTURE OF DEVELOPING LATEX DUCTS IN MAMMILLARIA GUERRERONIS (CACTACEAE)

The schizo-lysigenous latex ducts of Mammillaria guerreronis, sect. Subhydrochylus, were examined by optical and electron microscopy. These ducts are complex having a distinct outer epithelium without intercellular spaces and an inner epithelium in which schizogenous spaces arise. Schizogeny begins with formation of bulbous pockets and/or production of dark streaks in certain walls. Spaces formed by these processes ultimately contain a combination of electron dense materials, vesicles, and numerous thin, convoluted wall layers. Schizogeny may be responsible for initial formation of lumen and latex and may also separate some inner epithelial cells from the surrounding layers. Lysigeny of the inner epithelial cells contributes materials to the latex and allows enlargement of the duct. The inner epithelial cells contain mitochondria, dictyosomes, apparently functional nuclei, and numerous vesicles. The outer epithelium has fewer vesicles than the inner epithelium. Schizo-lysigeny in the members of sect. Subhydrochylus is considered to be ancestral to the strict lysigeny of the members of sect. Mammillaria. The inner and outer epithelia of M. guerreronis are thought to be homologous to the lumen and epithelium respectively of M. heyderi.     

Changes in microfibril arrangement on the inner surface of the epidermal cell walls in the epicotyl of Vigna angularis ohwi et ohashi during cell growth

Throughout the entire period of cell growth, the microfibrils on the inner surface of the outer tangential walls of the epidermal cells of Vigna angularis epicotyls are running parallel to one another and their orientation differs from cell to cell. Although transverse, oblique and longitudinal microfibrils can be observed irrespective of cell age, the frequency distribution of microfibril orientation changes with age. In young cells, transversely oriented microfibrils predominate. In cells of medium age, which are still undergoing elongation, transverse, oblique and longitudinal microfibrils are present in quite similar frequencies. In old, non-growing cells, longitudinally oriented microfibrils are predominent. A decrease in the relative frequency of transversely oriented microfibrils with cell age was also observed in the radial epidermal walls.     

Contributions of the surface of the root tip to the growth of Zea roots in soil

The development of the epidermal layer of roots of Zea is traced from the quiescent centre to the zone where root hairs develop. In the zone of cell division a three layered coat forms on the outside of the epidermal cells consisting of the outer epidermal walls, overlaid by a two-layered pellicle composed of a thick fibrillar inner layer of polysaccharide, and a thin fibrillar outer layer of protein. The epidermal cells divide several times in the same longitudinal file but rarely across a radius to give a new longitudinal file. Thus, the radial walls become much thicker than all but the original transverse walls, and packets of up to 32 daughter cells derived from a single initial may be distinguished. The pellicle develops during these divisions as a continuum over the outer walls of the daughter cells. It is proposed that the pellicle provides a stiffening to the forward end of the root which permits it to penetrate soil without bending. Support for this hypothesis is shown by the Zea mays mutant Ageotropic in which the pellicle is absent, the epidermal surface is disorganized, and which grows crookedly through soil. In the zone of extension growth of normal roots of two Zea species the pellicle thins and disappears. Circumferential strips of the pellicle were peeled off the young epidermal cells and could be stretched to twice their length. This deformation is partly the result of the pellicle stretching and breaking above the attachments of the radial walls. After normal thinning of the pellicle, detachment of the radial walls at their outer ends produces a corrugated surface in the proximal zone of the root tips. In dicotyledons (e.g., soybean), there is no similar pellicle, but a stiff root tip is produced by a long multi-layered root cap, the proximal portion of which covers the elongating epidermal surface.     

Ultrastructure of spore development in <Emphasis Type="Italic">Scutellospora heterogama</Emphasis>

The ultrastructural detail of spore development in Scutellospora heterogama is described. Although the main ontogenetic events are similar to those described from light microscopy, the complexity of wall layering is greater when examined at an ultrastructural level. The basic concept of a rigid spore wall enclosing two inner, flexible walls still holds true, but there are additional zones within these three walls distinguishable using electron microscopy, including an inner layer that is involved in the formation of the germination shield. The spore wall has three layers rather than the two reported previously. An outer, thin ornamented layer and an inner, thicker layer are both derived from the hyphal wall and present at all stages of development. These layers differentiate into the outer spore layer visible at the light microscope level. A third inner layer unique to the spore develops during spore swelling and rapidly expands before contracting back to form the second wall layer visible by light microscopy. The two inner flexible walls also are more complex than light microscopy suggests. The close association with the inner flexible walls with germination shield formation consolidates the preferred use of the term ‘germinal walls’ for these structures. A thin electron-dense layer separates the two germinal walls and is the region in which the germination shield forms. The inner germinal wall develops at least two sub-layers, one of which has an appearance similar to that of the expanding layer of the outer spore wall. An electron-dense layer is formed on the inner surface of the inner germinal wall as the germination shield develops, and this forms the wall surrounding the germination shield as well as the germination tube. At maturity, the outer germinal wall develops a thin, striate layer within its substructure.     

Sand rhizosheath of an arid zone grass

Summary The root sheath of the arid zone grassZygochloa paradoxa comprises a dense cylinder of sand grains held mainly by short twisted root hairs. The sand sheath and hypodermal sleeve enclose a thick cortex with a sclerenchymatous inner zone and a partially disintegrated aerenchymatous outer zone. The outer tube comprising sheath and hypodermal sleeve is largely impermeable to water and its primary function is probably to insulate the stele against moisture loss during translocation.     

Electron microscopic observation of cell wall structure during appressorium formation in Colletotrichum lagenarium

Summary The formation of cell walls during the appressorium formation inColletotrichum lagenarium was observed by electron microscope on the materials prepared by replicas and sectioning. The outer layer of conidia cell walls ruptured at the time of germination and the inner layer bulged out to form a germ tube. The germ tubes and primordia of appressoria had smooth surface and were consisted of one-layered cell wall. However, as the appressorium matured, the electron dense materials appeared on the outer surface of the cell wall which grew into granules. These granules are believed to form the outer layer of appressoria. The under side of the appressorium in contact with the glass surface showed a round pore.Contribution No. 191.     

OCCURRENCE OF TRI-LAMELLAR BODIES IN ISOLATES OF NOSTOC (CYANOPHYCEAE)1

Tri-lamellar bodies were observed in eight of 29 isolates of Nostoc examined. They appeared identical to the previously described bodies in various species of Anabaena. The bodies consist of three discoid lamellae each ca. 0.3 μm diam and 8 nm thick. The outer lamella (closest to the plasma membrane) is separated from the middle lamella by a 12 nm space whereas the middle and inner lamellae are ca. 8 nm apart. Osmiophilic striations 3 nm wide were generally observed running between the lamellae. Osmiophilic β granules were usually associated with the inner lamella. The bodies were most always located close to the plasma membrane along the longitudinal wall near the junction of the cross and longitudinal walls. In three isolates the bodies located near the cross walls were associated with gas vesicles and possessed a slightly different morphology. These tri-lamellar bodies consisted of three discoid lamellae, each ca. 2 nm thick, ca. 25 nm apart with electron dense material between the inner and middle lamellae. Pores 20 nm diam and ca. 60 nm apart were observed in layer 2 of the cell wall adjacent to the tri-lamellar bodies. These wall pores were also observed in isolates lacking tri-lamellar bodies.     

Histological organization of the intestine in the crayfish Procambarus clarkii

Six longitudinal ridges span the length of the intestine in the crayfish Procambarus clarkii. A simple columnar epithelium with tetralaminar cuticle lines the lumen. Folds of the epithelium overlie a dense irregular connective tissue packed with mixed acinar (alveolar) glands. Mucous secretions are probably involved with formation and lubrication of faecal strings; neither the nature nor the role of the serous secretions is immediately apparent. Aggregations of cells with large cytoplasmic vacuoles, called bladder cells, appear in the subepithelial connective tissue near the tops of the intestinal ridges. The bladder cells are suitably positioned to bolster the integrity of the ridges. Striated muscle of the intestine occurs in inner longitudinal and outer circular layers. The inner longitudinal layer consists of six strips, with one strip associated with the base of each intestinal ridge. The outer circular layer is essentially complete, but there are periodic apertures in this layer on the left and right sides of the intestine, providing nerves and haemolymph vessels with access to the interior of the gut. Based on histological features, and consistent with reports on other crayfish, we conclude that the intestine of P. clarkii has a proctodeal (ectodermal) origin.