摘要:

Experimental hybridization, cytogenetic observations, flower pigment analyses and scanning electron microscope observations of seed coat features were used to investigate the relationship betweenL. annuusL. andL. hierosolymitanusBoiss. Pod width, seed size, shape and surface ornamentation proved to be good diagnostic criteria for distinguishing the two taxa. Hybridization between various accessions of the two species revealed variation both between and within accessions. Enhanced anthocyanin levels were detected in the standard petals of the reciprocal hybrids made between two specific accessions ofL. annuusandL. hierosolymitanus.The results of the investigations support the retention ofL. annuusandL. hierosolymitanusas separate species.

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1996.tb02066.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The Devonian herbaceous lycophyte genusHaskinsiaGrierson and Banks is characterized by narrow dichotomizing stems and helically arranged petiolate leaves with a broad, approximately deltoid, lamina. New specimens are reported from four horizons in the Lower Member of the Campo Chico Formation, Sierra de Perijá, western Venezuela.H. sagittakaEdwards and Benedetto has sagittate leaves, and fertile specimens are reported for the first time; the ellipsoidal/obovoid adaxially‐flattened sporangium is attached to unmodified leaves towards the top of the petiole in the adaxial position.H.sp. has sagittate leaves which are larger than any yet attributed to the genus but is represented by only three specimens.H. hastatasp. nov. has hastate leaves; the sporangia are more globose but positioned similarly to those ofH. sagittata.The occurrence of the sporangia on unmodified microphylls indicates thatHaskinsiais a member of Protolepidodendrales. The status of Haskinsiaceae is discussed.The Venezuelan specimens are compared with other records of HaskimiandHaskinsia‐like plants from North America, Kazakhstan, North China, North Africa and Antarc

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1996.tb02067.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

A comprehensive treatment of the north‐west African genusNwelleaB.H. Wilcoxet al.(Compositae, Anthemideae) is presented, including an emended generic description. Its sole species,Nivellea nivellei(Braun‐Blanq.&Maire) B.H. Wilcoxet al.is lectotypified. Morphological, anatomical and cytological features of this species are reported. Its distribution is map

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1996.tb02068.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

A comparative study was undertaken on the leaves and petioles of 16 speciesof Mallotusin order to investigate anatomical variations of potential in species identification. There is a range of characters which varies between species. These include the outline of the midrib and petiole in transverse sections, the shape of the vascular tissue in midribs, the presence of central bundles in the petiole, the presence of terminal sclereids, enlarged tracheids, presence or absence of non‐glandular trichomes, and parenchymatous sheaths in vascular bundles. A combination of these characters may be used to identify species. Anatomical data support the placing of only a few species into the respective section

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1996.tb02069.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

A supposed hybrid population (Agave peacockii) betweenAgave marmorataandAgave kerchoveiin a semiarid ecosystem at Zapotitlán Salinas, in the Mexican State of Puebla, was investigated, and its hybrid status corroborated in morphometric terms. A Stepwise Discriminant Analysis of the ratios: Number of leaved Rosette diameter, Leaf width/Leaf length, Number of spines/Leaf length, Distance between the upper spine and the tip of the leaf/Leaf length, and Distance between the upper spine and the tip of the leaf/Number of spines, supported our hypothesis of the existence of these naturally occurring hybrids, which are intermediate and distinct from the parental species. A null model was constructed to contrast the real case with a possible artifact, and the results also supported our hypothesis. The possible meaning of this kind of hybridization is discussed

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1996.tb02070.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Darlington's recombination indices were calculated for eight species ofErythinaby adding the mean chiasma frequency and the haploid chromosome number of each species. The recombination indices distinguished subgenusErythraster(two species with greater mean chiasma frequency) from subgeneraMicropteryxandEythrina.This discrimination corroborates literature data on pollen morphology. It was not possible to separate groups at sectional level using recombination index. The recombination indices were also compared with data on breeding system and pollinators, available in literature, to investigate Grant's hypothesis on the occurrence of compensatory mechanisms in the regulation of recombination in plants. The data on breeding systems inEythrinaare very incomplete and it was not possible to correlate values of recombination indices with autogamy or allogamy. Species visited by hummingbirds showed lower recombination indices than species visited by other kind of pollinators.

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1996.tb02071.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The development of the microsporangium and male gametophyte of three species ofPodocarpuswas studied with light microscopy (LM) and the morphology of pollen with scanning and transmission electron microscopy (SEM and TEM). During early stages, the male cone is covered with coriaceous scales. The archesporid cells go through a dormant period. Later the pollen mother cells differentiate and undergo meiosis. Callose is detected around the tetrad and between each monad. The microspore nucleus divides several times to give rise to a multicellular gametophyte, which includes the tube cell, the stalk and body cells, and four prothallial cells. The exine of the pollen grain is rugulate in the corpus and quite smooth in the sacci. The ultrastructure of the pollen wall consists of the alveolate sexine, the laminate nexine I and the amorphous nexine II. The intine is very thin. Comparison of the mature grain of some fossils with living members of the Podocarpaceae reveals great similarity.

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1996.tb02072.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY