摘要:

SUMMARYThe morphology of field‐collected plants ofAcrochaetium densum(Drew) Papenfuss from the Dutch coast is described in some detail. This species is characterized by a persistent septate spore, a multicellular filamentous prostrate part and numerous rather short erect axes, which are secundly branched in mature plants. Reproduction takes place by mono‐spores which are typically formed in rows of two or three successive monosporangia, ripening simultaneously.In culture the plants also formed tetrasporangia and subsequently the life‐history could be completed. It appeared to be a diplobiontic cycle consisting of morphologically dissimilar generations: the unisexual gametophytes have a unicellular base from which 1–5 erect filaments arise. The life cycle seems to be mainly temperature‐controlled.From experiments in crossed light and temperature gradients it could be concluded that spore germination and dimensions of cells and sporangia are the least modifiable and hence the most useful characters in delimiting the species from other acrochaetioid taxa.The nameAcrochaetium densumwas chosen rather arbitrarily. Identification of both the tetrasporophyte and the gametophyte presents considerable difficulties: a large number of described species shows resemblance to one or the other g

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1976.tb00239.x

年代:1976

数据来源: WILEY

摘要:

SUMMARYIndications of the existence of plants ofSilene otitesin the dunes in The Netherlands (Coastal plants), with wind pollination additional to insect pollination, gave rise to this study. Morphological evidence, such as stickyness of pollen, together with field observations on the wind dispersal of pollen and experiments with bagged flowers, prove the absence of wind pollination. Insect visitors mainly belonged to the Lepidoptera (Microlepidoptera, Geometridae and Noctuidae) and to the Diptera (Culicidae). Observations of the dusting with pollen and of the flower visiting behaviour indicate that insects of these two types pollinate. This has finally been proved by experimental confinement of insects with bagged flowers. Neuroptera are visitors but are not pollinators. The pollination of flowers by mosquitoes is new for Europe.

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1976.tb00240.x

年代:1976

数据来源: WILEY

摘要:

SUMMARYIn this paper the results of a palynological investigation of the 30–78 m interval from a deep bore hole in the Tenagi Philippon are presented. The pollen diagram reflects alternating steppe phases and phases of oak forest, some of them with an evergreen character. Taking the14C dated last interglacial‐glacial cycle (resp. forest and steppe) as a model, the oak phases are interpreted as interglacials or warm interstadials and the steppe phases mostly as glacials.The presence of pollen from evergreen oaks indicates warmer periods that might be called interglacials whereas the presence of only pollen from (semi) deciduous oak species indicates periods that might be called interstadi

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1976.tb00241.x

年代:1976

数据来源: WILEY

摘要:

SUMMARYRed light causes an increase of auxin export from subapical sections ofAvenacoleoptiles and simultaneously decreases the export from tips. Also the imposition of a physical barrier on the export of auxin from tips results in a reduced export of auxin after the barrier has been removed. This shows that red light may exert an influence by way of changes in transport properties in the coleoptile.

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1976.tb00242.x

年代:1976

数据来源: WILEY