摘要:

A seven‐year study of a stand of the endemicScalesia pedunculata(Asteraceae), which is the dominant tier ill the humid forest on the island oS Santa Cruz, Galápagos, reveals a characteristic pattern of growth and survival. TheScalesiatrees initially show a rapid increase in both height and girth. After approximately 34–56 years the trees may reach 7–8 m in height and start producing flowers; the relative increase in girth then becomes more pronounced. The mortality rate is very high during the first 4–5 years, decreasing thereafter as the individuals age. It is suggested that the growth and survival pattern ofS. pedunculatais an expression of an adaptive strategy fitted for a pioneer or early‐successional tree. This tree is simultaneously able to persist in the community by the means of a large reproductive effort and a rapid population turnover. The method of seed‐dispersal in the genus discussed in relation to the gr

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1979.tb02186.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

The anatomy of the assimilating stems of three brooms (Fabaceae) all show distinct xeromorphic features in their tissues, but these are developed to different degrees. The epidermis consists of very thick, cutinized outer walls, deeply sunken stomata, and a dense layer of trichomes, at least in younger steins. In older sterns some of the stomata are blocked by cell‐plugs. The chlorenchyma is multilayered. The main supporting tissue consists of peripheral gelatinous fibre strands. It is argued that these may function in water storage. Parenchymatous water storage cells are present in the pith of two species. The structure and function of the xeromorphic features are discussed in relation to the ecology of the plant

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1979.tb02187.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Triphyophyllum peltatum(Dioncophyllaceae), a tropical‐West African liane, is heterophyllous, bearing leaves of three types, two on juvenile, non‐climbing, short shoots, and the third on the mature axis. The short shoots produce mostly eglandular, lanceolate leaves, but just before the height of the rainy season small clusters of relatively ephemeral, glandular, filiform leaves are formed. These glandular leaves bear both stalked and sessile glands, and they act as efficient trapping organs for the prey, mostly flying insects and other small animals. The stalked glands, of which there are two size classes, are the most anatomically elaborate known in the plant kingdom. Structurally there are similarities with the stalked glands ofDrosophyllumandDrosera.At maturity they carry secretion droplets, and stimulation by the prey leads to further secretion. The secretions contain a range of hydrolytic enzymes.During sonic periods of its developmentTriphyophyllumis probably carnivorous. An important source of nutrients is thus tapped which could be significant in making possible an earlier transition from the juvenile to the rapidly‐climbing adult form.The Dioncophyllaceae, contains two other monotypic genera, neither with the carnivorous habit.Triphyophyllumis considered as an ecological African analogueof Nepe

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1979.tb02188.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Many inflorescence bracts ofPelargonium × hortorumare hypoascidiate, i.e. congenitally outrolled into funnel‐shaped structures. Their stalks are unifacial but bounded all round by the morphologically adaxial surface of the bracts. Their single bundles may be vasicentric, with xylem encircling phloem. All intermediate stages occur from conventional flat to hypoascidiate bracts. This seems to be the clearest instance of hypopeltate bracts, and perhaps the only well‐established

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1979.tb02189.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

The structure and growth of the seedling, as described in the literature, is discussed for both monocotylar Dicotyledones and for Monocotyledones (several Apiaceae, Ranunculaceae and Gesneriaceae; species ofCombretum, Peperomia, Cyclamen, CorydalisandPinguicula, and also anomalous syncotylar examples ofImpatiens, Butomus, Agave, Cordyline, Dioscorea, PitcairniaandCostus). In all examples the single cotyledon appears to be derived, phylogenetically, from an ancestral pair which has fused, often with no remaining trace of their double origin, to give an apparatus which buries the unexpanded plumule and radicle deeply in the ground early in germination. No evidence for suppression of one of the ancestral pair of cotyledons was found in any species.The syncotylar theory of the origin of monocotyledons of Sargant (1903) is supported and extended to apply to all known monocotylar species. The anomalous appearance of paired cotyledons inAgapanthusandCyrtanthusapparently results from twinning, as known inSinapisandCentranthus, not to atavistic reformation.

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1979.tb02190.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY