摘要:

Pollen morphology is described for 39 (of the ca. 56) species ofLagerstroemia(Lythraceae). Different pollen types are associated with different stamen whorls, and a complete characterization of the pollen, as a contribution to an overall taxonomic data base for the genus, requires recognition of both variants within individual species. The majority of species (82%) display dimorphic stamens with dimorphic pollen. Dimorphic stamens with monomorphic pollen occur in five species and mono-morphic stamens with monomorphic pollen in two species. Intuitive groupings and phenetic analysis give results of taxonomic interest, including the following: 1) the shared monomorphic stamen/monomorphic pollen condition ofL speciosaandL macrocarpahas not been considered indicative of close relationship, and this is supported by the distinctiveness of their pollen, 2) there is a general correlation of pollen groups with the present three-section classification, 3) pollen of three species of sect.Lagerstroemiadiffer from the rest by their small size, thin exines, and indistinct margo, whereas at the same time pollen, of 10 species is extremely similar indicating exceptionally close species relationships, 4)L duperreanais misplaced in sect.Adambeaand on the basis of similar pollen and other features, should be transferred to sect.Trichocarpidium. Suggested evolutionary trends are toward the presence of pseudocolpi, a more uniformly psilate tectum, a more spherical shape, a distinct margo, reduction of the colpus, and monomorphic pollen (paralleling reduction from dimorphic to monomorphic stamens).

ISSN:0017-3134    

DOI:10.1080/00173139409427452

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The pollen of twenty-six of the thirty taxa (specific and infraspecific) of the genusSideritisL. subgenusMarrubiastrum(Moench) Mend.-Heuer (Lamiaceae) endemic to the Macaronesic region, was studied by optical and scanning electron microscopy. This study was performed to evaluate the possible taxonomic utility of the seemingly absent palynological data for the taxa of this endemic subgenus.

ISSN:0017-3134    

DOI:10.1080/00173139409427453

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The occurrence and ecology of three species of Ragweed (AmbrosiaL.) in Britain is described.Ambrosia artemisiifoliaL. is the commonest species and is most often introduced with bird seed, but does not persist probably due to climate limitation of seed production and germination. A.psilostachyaDC. is rarely established in sandy places.A. trifidaL. is an uncommon introduction which also does not persist. Ragweed pollen was regularly recorded in Britain in 1992. Under conditions of global warming, it is likely thatA. artemisiifoliawill become established in Britain and could cause widespread hay fever.

ISSN:0017-3134    

DOI:10.1080/00173139409427454

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Differing interpretations of sporoderm development in megaspores ofSelaginellahave resulted in confusion surrounding use of the term mesospore. Different ontogenetic events result in one of two distinct structural types in the innermost exospore. The first type consists of a thin, highly compressed layer (referred to as an inner separable layer; ISL) which separates, along with the endospore, from the remainder of the overlying exospore. This layer forms if a viable protoplast persists in the megaspore. Growth of the viable protoplast compresses the ISL tightly to the inside of the overlying exospore although a line of separation can still be detected even in fully mature megaspores. The second structural type, which may be termed a “mesospore proper”, develops if the protoplast aborts. In the latter case, there is evidence to suggest that the aborting protoplast adds additional material (if only residues of cellular autolysis) to the inside of the mesospore. This protoplast abortion and deposition of the products of cellular autophagy characterize the mesospore and result in the formation of structural features which can be used to recognize mesospores in modern and fossil megaspores. These features include: 1) a two layered organization, 2) little compression (some free space present) and 3) a greater thickness than the ISL. Recognition of a mesospore should be based upon the presence of all three of these features.

ISSN:0017-3134    

DOI:10.1080/00173139409427455

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The extraction and identification of pollen grains from core samples taken from a beeswax statue is described. The samples contained only small amounts of pollen compared to a recent sample of commercial beeswax. Ten pollen types were identified. The most abundant wereOnobrychis, CylisusandTrifolium. Anchusa, Campanula, Centaurea, Chenopodium, JuniperusorCupressus, Pinusand Labiatae were present in small quantities. In broad terms, the results suggest that the beeswax was produced by bees foraging in a cornfield, or cultivated land, probably in southern Europe, before the widespread use of herbicides.

ISSN:0017-3134    

DOI:10.1080/00173139409427456

出版商:Taylor & Francis Group    

年代:1994

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:10.1080/00173139409427451

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor