摘要:

VON TEICHMAN, I.&VAN WYK, A. E., 1991. Trends in the evolution of dicotyledonous seeds based on character associations, with special reference to pachychalazy and recalcitrance. The possible evolutionary status of the endothelium, hypostase, pachychalaza and the recalcitrant viability behaviour of seeds is considered in relation to bitegmy/unitegmy, crassinucellate/tenuinucellate ovules, nuclear/cellular endosperm development, large/small seed size, woody/herbaceous habit and tropical/temperate habitat. The presence of the endothelium, hypostase, pachychalaza and recalcitrance in dicotyledonous families is plotted against Dahlgren's system of classification. Results are compared with Sporne's advancement index for the various families. An endothelium is considered derived since it occurs more often in highly evolved superorders and is significantly associated with derived ovule and endosperm character states as well as with smaller seed size. A hypostase appears to be relatively ancestral and is significantly associated with pachychalazy and recalcitrance. The endothelium and hypostase have developed independently in many taxa and could be interpreted as being structurally and functionally analogous. Pachychalazy and recalcitrance are significantly associated with ancestral ovule character states and, at the species level, with large seed size (overgrown seed), woody habit and tropical habitat. The presence of pachychalazy, recalcitrance and associated large seed size are therefore regarded as ancestral character states of the dicotyledons. Consideration of currently accepted dicta on seed character state polarity, suggests a reversal in the evolutionary status of pachychalazy and large seed size.

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1991.tb00205.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

KORDOFANI, M.&INGROUILLE, M., 1991. Patterns of morphological variation in theAcaciaspecies (Mimosaceae) of northern Sudan. A numerical taxonomic review has been carried out on the morphology of northern Sudanese Acacia species. Fifty‐one characters were scored from 12 species sampled at 12 sites. There is evidence of large scale population variation. Within a single site species are distinct but a comparison of plants between different sites may obscure species differences. Each species has a peculiar local variant in each sampled site, even when sites are separated by only a few kilometres. The possible significance of this pattern of variation is discussed. Species complexes are delineated and useful species diagnostics describe

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1991.tb00206.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

RONSE DECRAENE, L.‐P.&SMETS, E., 1991. The impact of receptacular growth on polyandry in the Myrtales. The androecium of the Myrtales shows a wide variation in structure and development, linked with an original diplostemony. The difference between a centrifugal stamen inception in Lythraceae against a centripetal inception in other families has been a major issue in discussing the internal relationships of the Myrtales. The first stamens usually arise as pairs opposite the petals on primary androecial primordia. It is shown that the number of stamens that are initiated and the difference between the direction of development of more stamens are based on the extent of growth of the receptacle after the inception of the primary androecial primordia. InLagerstroemia indica, receptacular growth takes place between stamens and petals providing room for a centrifugal development. In the Punicaceae and Myrtaceae growth of the receptacle occurs between the androecium and gynoecium, leading to a centripetal development of the stamens. The development of a ring‐wall is discussed and a comparison is made with other types of complex polyan

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1991.tb00207.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ELLISON, J. C, 1991. The Pacific palaeogeography ofRhizophora mangleL. (Rhizophoraceae). The American red mangrove,Rhizophora mangleis disjunct in its occurrence between the Neotropics and an outlier in the south‐west Pacific, a distribution which has been speculated upon for over a century. The species is shown to be indigenous in Tonga, the first such evidence from the outlier, with certain identification of abundantly occurring pollen in an early Holocene mangrove peat, that pre‐dates the arrival of man by some 2500 years. It is suggested from review of world‐wide fossil records that the species crossed the Pacific eastwards during the Eocene, facilitated by land connections resultant from low stands of sea level and before major subsidence of the Pacific plate. Then subsidence of the Pacific plate caused local extinctions on islands of the central and eastern Pacific as they periodically submerged, the species not able to recolonize from either refuges west of the Andesite line or America due to loss of land connections and its poor dispersal capab

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1991.tb00208.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

LESTER, R. N.&EZCURRA, C, 1991. Enzyme etching treatment as an aid in the study of seed surface sculpture inJusticiaandRuellia(Acanthaceae). Enzyme etching treatment of seeds ofJusticiawas tested before scanning electron microscope examination. On all species tested the treatment removed the outer periclinal walls of the epidermal cells of the seeds, revealing the shape and morphology of the anticlinal walls. This treatment provides additional characters of the structure of the testa that may be useful in assessing relationships between species in this large and complex genus, but it proved useless inRuellia.Here the seeds produce a coat of mucilage when moistened that completely protects the testa from the action of even extensive enzyme treatment.

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1991.tb00209.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY