摘要:

Three morphological problems were investigated in three species of the Nyctaginaceae: epiphylly, phyllotaxis and placentation. Epiphylly, which occurs inBougainvillea spectabilis, is the result of ontogenetic displacement resulting from the activity of an intercalary meristem at the base of the floral bract and the floral bud. Floral development ofBougainvillea spectabiliswas compared with that ofBoerhaavia diffusaandMirabilis jalapa. Considerable variation occurs with regard to the number and arrangement of stamens. Five stamens are initiated simultaneously, alternate to the petals, inMirabilis. InBougainvillea, eight stamens arise sequentially at divergence angles suggestive of a 3/8 spiral. No developmental evidence was found to support the derivation of the eight stamens from a two whorled pentamerous androecium.Boerhaavianormally has only two stamens which most frequently are initiated toward opposite sides of the floral apex, but may also be formed in a 2/5 to 3/8 divergence. In some flowers only one or three stamens are formed. The gynoecium is formed in the same way in all three species: growth occurs in a crescent‐shaped zone at the periphery of the floral apex thus producing the gynoecial wall. The single ovule, which is basal in the mature gynoecium, is formed from the gradual upgrowth and transformation of the floral apex and is developmentally terminal. Even the two‐layered tunica is maintained as the floral apex is transformed into the ovule primordium. If ‘carpel’ is defined traditionally as a folded megasporophyll which bears and encloses ovule(s) then carpels are not present in the gynoecia of the three species studied. If ‘carpel’ is re‐defined as an appendage which encloses ovule(s), then the gynoecia of the Nyctaginaceae are carpellate. However, the ovules remain cauline regardless of which definiti

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1982.tb00532.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

The surface sculpturing of the pollen of some species of the taxonomically widely separated generaHarpalyce(tribe Brongniartieae),Camoensia(tribe Sophoreae),Millettia(tribe Tephrosieae), and of the monotypicDahlstedtia(tribe Tephrosieae) which have large red or white flowers adapted for pollination by birds or bats, is coarsely rugulate or verrucate. Related taxa with small insect pollinated flowers have pollen with simple reticulate or perforate surface sculpturing. The exine stratification ofAlexaandCastanospermum(tribe Sophoreae), genera with large red bird‐flowers, is complex with a layer of tectal columellae and differs from that of other genera in the tribe Sophoreae which have a normal pollen wall structure. These modifications of pollen structure and sculpture appear to be the result of convergent evolution and a secondary adaptation to pollination. The taxonomic and functional significance of the observations are briefly discusse

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1982.tb00533.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

The settlement of Australia by European man has been a major ecological factor in the history of the vegetation. A reconstruction of one aspect of this influence is given, based on estimations of the growth rate and flowering history of a population ofXanthorrhoea johnsonii.The age structure of four parts of the existing population within the campus of Griffith University, Brisbane was examined. The mean growth rate, based on counts of leaf production and the number of leaf scars per unit length of the caudexes, was estimated to be 0.88 (s.d. 0.17) cm year‐1. The flowering history was reconstructed from the numbers and positions of flower scars recorded after removal of the leaf bases from 264 individuals. Flowering potential appears to increase up to about 50 years of age and is then relatively stable. Flower production gradually increased from 1820 to 1967 and then fell sharply. Since 1840 there is a strong correlation between the number of residences established within 3 km of the site and the number of flowers produced. The number of plants flowering is known to increase as a result of fire, and we therefore suggest that increasing numbers of accidental or deliberate fires started by settlers and later inhabitants may have caused the increase in flowerin

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1982.tb00534.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

The arrangement of lateral insertions has been examined on axes ofStigmaria ficoides. The arrangement can be considered as a phyllotactic pattern made up of parastichies and orthostichies. Orthodox phyllotactic patterns, based on parastichy numbers from the Fibonacci or common accessory series, do not occur. Instead spiral (or multijugate) arrangements occur based on pairs of parastichy numbers such asxandx+ 1,xandx+ 2,xandx+ 3, etc. andxranges from 12 to 19. Whorled arrangements occur relatively infrequently. Individual axes commonly show frequent changes in pattern. The observations are used to make deductions about the growth and homology of stigmarian axes.

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1982.tb00535.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

A wide variety of cuticles and tubular elements is described from a late Silurian (Ludlow Series) locality in Wales which has already yielded a macroflora containingCooksoniaLang,SteganothecaEdwards and vascularized axes. These microfossils are compared with Lang's Downtonian.Nematothalluscomplex and Silurian assemblages of similar composition from north America. It is concluded that the majority of these microfossils derive from non‐vascular plants of uncertain affinity which lived on lan

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1982.tb00536.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

The genusMerremiais found in the tropical regions of both hemispheres. The climbing species with fast growth rates can become troublesome weeds of cultivation and forestry. ServeralMerremiaspecies have become serious weeds of forestry plantations in the Solomon Islands. The important species are discussed and a new species,Merremia bracteata, found inMerremiainfestations is described.

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1982.tb00537.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY