摘要:

The pollen morphology of the Nyctaginaceae, a family of approximately 30 genera and 250–300 species, is extremely varied and contains the following general types: pantoporate grains with tubuliferous and spinulose sexine pattern; 3–4-colpate grains with coarse reticulate sexine patterns; 3-colpate grains with tegillate sexine patterns; 6-colpate grains; 12–15–18-panto-colpate grains; and 12-pantoporate grains. Detailed descriptions, scanning micrographs, and a discussion of taxonomical relevance are provided for the tribe Nyctagineae (Mirabileae).

ISSN:0017-3134    

DOI:10.1080/00173137009427388

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

This study presents a detailed survey and discussion of the fine structure ofAmbrosiapollen. Representatives from all evolutionary groups and geographical regions are used, including 37 species and four hybrids. No significant differences are found among the species, a circumstance supportive of the congeneric nature ofAmbrosiaL. andFranseriaCav. hypothesized earlier from other evidence. The similarities of the pollen ofAmbrosiato that of the Heliantheae and Anthemideae are discussed. Newly observed structural features of the polar and colpal regions are pointed out which support an intermediate position of the Ambrosieae between the Heliantheae and Anthemideae. Possible specializations ofAmbrosiapollen within the tribe are suggested. The data also indicate that among the three closely related genera,Ambrosia, XanthiumandHymenoclea, the relationship ofAmbrosiatoHymenocleais closest.

ISSN:0017-3134    

DOI:10.1080/00173137009427389

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The formation of the saccus begins while the pollen grains are still within the tetrad, surrounded by the callose wall. Material giving a clear periodic acid-Schiff reaction accumulates between the early sexine and the plasma membrane at the sites of the future sacci. This material is subsequently isolated from the protoplast by the nexine. After dissolution of the callose wall and separation of the grains, the PAS-positive material expands to many times its initial volume, widely separating the nexine and sexine, and so forming the saccus. The saccus thus lies within the exine. Electron micrographs indicate that the PAS-positive material involved in saccus formation comes from golgi vesicles. The reason for the expansion of this material after the separation of the grains remains unknown. Expansion of the sacci is accompanied by increase in thickness of the sexine elsewhere. It is therefore concluded, since some PAS-positive material is present throughout the primexine in addition to the concentrations at the sites of the sacci, that these should be interpreted as local modifications of normal exine structure, and not as entirely new features of the wall.

ISSN:0017-3134    

DOI:10.1080/00173137009427390

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

Bryophytic spores of eight genera in the sub-order Jungermanniales acrogynae have been examined by transmission electron microscopy. The spores are alete and subisopolar, ranging in size from 8–50 μ. Although most of these spores are indistinguishable from one another under the light microscope, great variation of wall structure can be detected at the electron microscope level. Three elements of fine structure are defined: sheet lamellae, slip lamellae and microgranules. Slip lamellae are found in all eight spore types, but sheet lamellae are lacking in the Lophocoleaceae. The lamellae have a thickness of 20–30 nm with a central low-dense region about 4 nm thick. A homogeneous sporonine material is present in walls ofRadulaandFrullaniaspores. Similar wall ultrastructure is exhibited among members of a family; two genera have been studied from each of the families Lophocoleaceae and Cephaloziaceae. Preparative techniques are discussed and comparisons drawn with the fine structure of pollen walls.

ISSN:0017-3134    

DOI:10.1080/00173137009427391

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

Four types of cells are present in the young gametophyte: basal, rhizoidal, apical prothallial and intermediary prothallial cells. A description of the fine structure of these four different cell types is given. The primary storage products in the spore cells are lipids and proteinaceous substances. These are used up during germination. The quantitative disposition of the organelles and storage products are described.

ISSN:0017-3134    

DOI:10.1080/00173137009427392

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

Following X-ray treatment of seeds ofTrigonella foenum-graecum(subject to doses of 25000, 50000 and 75000 R units besides control) plants were grown to maturity and resultant pollen grains studied. Little pollen morphological variation regarding apertural condition, shape and surface pattern have been noticed. Variations in size of pollen grains were found, viz. up to the level of 50000 R a gradual decrease in the mean polar axis and equatorial diameter of pollen grains was noted, but 75 000 R had no further effect and the dose of 100000 R proved lethal for the seeds.

ISSN:0017-3134    

DOI:10.1080/00173137009427393

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The examination of spores belonging to eight species representing five genera of Polypodiaceae reveals that they are typically free, anisopolar and monolete (bilateral). In a majority of cases the spores are yellow and have a short laesura—about half the length of the greater equatorial axis of the spore. Generally, the spores are elliptical in polar view and plano-convex to concavo-convex in profile view but in cross section they vary in shape. The average measurements in equatorial plane range from 44 μ to 71 μ whereas in the polar direction they vary from 27 μ to 47 μ. The exine is thin (about 2.5 μ and nearly smooth (laevigose-scabrous-foveolose) inMicrosoriumandPhymatodesbut in the other investigated genera, it is thicker, possessing different types of projections. P: E varies from 4.6 to 5.5: 8. Oil globules are present in the spores of some species.

ISSN:0017-3134    

DOI:10.1080/00173137009427394

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

A method for the stratigraphical correlation and dating of Lower Cretaceous deposits from south-eastern France and north-eastern Spain is proposed, on the basis of a morphological analysis of pollen grains belonging to the form-genusClassopollis(Pflug) Pocock & Jansonius. This method has made possible correlations between microfloristic assemblages from various regions and it solves the problem of the age of the Wealden and Utrillas facies in the region studied. The correlation between these facies and the levels associated with bauxite suggests that a biostratigraphical interpretation would be possible by further application of the method described.

ISSN:0017-3134    

DOI:10.1080/00173137009427395

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue

ISSN:0017-3134    

DOI:10.1080/00173137009427387

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor