摘要:

Morphological and anatomical descriptions are given of the nodules present in the roots and stems of Dacrydium fonckii. Nodule structure is similar to that previously recorded for other Podocarpus‐type root nodules; the main difference being the absence of a nodular stele in D. fonckii. The widely accepted hypothesis that Podocarpus nodules are modified lateral roots is discusse

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1981.tb01222.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

The fine structure of the leaf nodules ofArdisia crispais described. The bacterial endophyte in mature nodules is extracellular, forming a compact mass which is encompassed within a 5–6 cell thick sheath of modified mesophyll cells. Processes from these sheath cells invade the bacterial mass providing a host surface across which exchange of metabolites may take place. Considerable pleomorphism is exhibited by the bacteria, paralleling that found in other symbiotic associations in which the host can influence the morphology of the microsymbiont. The spherical, highly granate chloroplasts, rich in starch, which are characteristic of the spongy mesophyll leaf cells, are replaced, in the modified sheath cells, by a degenerate plastid form containing membrane whorls. Lipid reserves appear to replace the starch in the sheath cells. The significance of these changes is discusse

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1981.tb01223.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Fossil leaves and bracteate fruits are described from a new Upper Palaeocene locality in the Reading Beds near Newbury, southern England. The leaves are assigned toCraspedodromophyllum acutumCrane and correspond in many respects to those of living Betulaceae. The bracts and fruits are assigned toPalaeocarpinus laciniataCrane, which although referable to the Coryleae exhibits a novel combination of the characters of several living genera, particularlyCorylusandCarpinus.An argument is presented for the association of these organs as a reconstructed fossil plant which is an extinct member of the Betulaceae. The evolution and fossil record of the Betulaceae are discussed, the late Upper Cretaceous and Palaeocene being regarded as the time at which the characters of modern genera were beginning to differentiate.Carpinusappears to have undergone a major Eurasian diversification during the late Palaeogene and early Neogene. Dispersal inPalaeocarpinus laciniatawas probably less specialized than in most extant Coryleae.

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1981.tb01224.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Two new names are published: Gibasis venustula subsp. robusta D. R. Hunt and Tradescantia poelliaeT). R. Hunt.

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1981.tb01225.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Species of theGibasis linearisalliance collected in Mexico in 1976 are shown to have a chromosome constitution ofx =6, butx =5 has also been found in some populations of G.rhodanthaandG. speciosa.These two basic numbers are associated with distinctive karyotypes, 2M + 4A and 3M + 2A respectively, which show a Robertsonian relationship with each other. The existence of 2n = 22 inG. speciosa, combining both basic numbers at the amphidiploid level provides evidence of pairing between metacentrics and acrocentrics in such a way as to substantiate the view that fusion or fission of chromosomes is responsible for the modification of basic number. This survey provides a basis for other studies which will determine the chromosome relationships of the species irrespective of chromosome number in this family.

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1981.tb01226.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

The five species ofTradescantiasectionCymbispathastudied, including one species T.poelliaeD. R. Hunt, have chromosome numbers ofIn =12, 14, 16, 22, 28, 30 and 36 and karyotypes of acrocentric, metacentric or telocentric chromosomes, or mixtures of both acrocentric and metacentric chromosomes. The numbers of major chromosome arms of these cytotypes give a nombre fondamentaP series of 14, 28, 42 and 56 which, in combination with meiotic analyses, indicates plants which, in genetical terms at least, are diploid, tetraploid, hexaploid and octoploid. This series has evolved from a 2n= 14 acrocentric or telocentric karyotype by a combination of Robertsonian fusion and polyploidy. Pseudo‐iso‐chromosomes are sometimes formed in this evolutionary development and can persist as stable members of normal compleme

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1981.tb01227.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1981.tb01228.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY