摘要:

Twelve petrified cupules containing seeds ofHydrasperma tenuisLong from the Upper‐Devonian/ Lower Carboniferous Transition Series from Ballyheigue, Kerry Head, Ireland have been studied. The cupules containing 2–6 seeds are borne in pairs. Each cupule is campanulate and composed of up to 24 oval to terete units. The axis of the cupule is forked, each resultant branch dividing in an alternate monopodial fashion producing six major axes. These divide repeatedly, each terminating in a narrow rounded tip. A reconstruction of a four‐seeded cupule is presented.Hydrasperma longiisp. nov. is proposed for the first ‘named’ Scottish cupulate seeds named by Long asHydraspermacf.tenuis. Hydrasperma longiidiffers fromH. tenuis:comparison ofH. tenuiswith other cupulate Lower Carboniferous seeds indicates that two major branching patterns of the cupule occur in early seed plants. Following an initial dichotomy, branching may either be entirely dichotomous, or alternately monopodial. The Aneurophytales appears to have the branching patterns consistent with its position as the ancest

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1980.tb01677.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

Cycads are pachycaulous plants possessing either aerial and columnar (arborescent) stems or subterranean and tuberous fleshy stems. In some taxa, such asZamia pumilaandStangeria eriopus, the vertical shoots are subterranean; the shoot apex usually remains underground even though new shoot increments arc added as a result of leaf development. The external surface of these stems has a winkled appearance in the distal regions and the height of the leaf scars decreases basipetally This is because both the fleshy tap root and the stem contract, pulling the shoot underground. This contraction results from the collapse of horizontal rows of cells in both the pith and cortex. The vascular cylinder which appears straight in longitudinal sections becomes sinuously distorted as this collapse of cells occurs.

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1980.tb01678.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

Individuals ofPhoenix dactyliferaL. have expanded pistillodes or pseudocarpels in staminate flowers. These pseudocarpels are located in the centre of the male flowers and are surrounded by stamens. The gynoecium has the characteristic three carpellate arrangement commonly found in female date palm flowers. Pseudocarpels from male flower buds can expand into parthenocarpic fruit. Histology of the expanded pistillodes or pseudotarpels is similar to that of normal carpels from pistillate plants. These pseudocarpels lack ovules. Nutrient medium containing 10 mg 1‐1of 2,4‐dichlorophenoxyacetic acid or p‐chlorophenylacetic acid and 0.3% activated neutralized charcoal enhanced the development and outgrowth of the pseudocarpels of cultured male fl

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1980.tb01679.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

Natural populations ofA bulbosusfrom three sites in southern England have been investigated and two were found to contain triploid and tetraploid plants in addition to normal diploids. Meiosis in the triploids was characterized by a high frequency of trivalent formation but, in the tetraploids, multivalents were formed at low frequencies and bivalents were the most common configurations. It is suggested that these are true autopolyploids that have probably arisen through somatic doubling since tetraploid cell lines were found in some anther loculi. The meiotic behaviour of the tetraploid plants is explained on the basis of bivalent‐promoting mechanisms being present in the diploid progenitor

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1980.tb01680.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

Chromosome counts are reported for 32 taxa (31 species and 1 subspecies) belonging to 10 genera of Commelinaceae from seven African and Asiatic countries. Counts for 13 species and 1 subspecies are recorded for the first time. Published chromosome numbers forAnhicopsisandPolyspathaare confirmed. It is suggested thatPdisota, PolliaandStanfieldidlaeach has a single basic number (x=20, 16 and 11, respectively). The known cytological diversity inFloscopais extended. The third continental African species ofColeolrypeis found to have the same chromosome number (2n = 36) as the other two. The preponderance of the basic number x = 15 inCommelinais supported. The uncommon basic number x=13 is reported in four taxa ofCyanotistogether with karyotypic differences. The basic number x=6 is found in a second species ofMurdannia. Karyotypic data in addition to chromosome numbers are presented for 24 of the 32 taxa investigated. Karyotypes are found to be useful in assessing relationships in the family, and evolutionary trends in the karyotype are noted.

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1980.tb01681.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

The classification of the Combretaceae in relation to the anatomy of the leaf epidermis (especially to trichomes) is surveyed, with particular reference toCombretum. The new combinationCalopyxis grandidieri(Drake) Capuron ex Stace is made and the new sectionCalopyxissect.PetalanthaStace is described. A sectional review ofCombretumis presented. The 69 sections are reduced to 45, and full bibliographic details, typification and synonymy are set out.

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1980.tb01682.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY