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We report on magnetotransport experiments performed at 4.2 K on hybrid structures consisting of a metal and a mesoscopic two-dimensional electron system in an InAs/InGaAs heterostructure. The devices were fabricated using cleaved-edge overgrowth. We find that they exhibit an extraordinary magnetoresistance effect (EMR) which is most pronounced in the case of the lowest specific contact resistance ρiof ≈10−8Ω cm2achieved in this work. The largest relative resistance change Δ R/R is 115,000% at a magnetic field B= 1 T. A systematic study of the performance of the EMR devices with down to sub-μm lateral dimension and with different ρiis reported.

Three new pottiaceous taxa from Israel, two species and one variety are described. Acaulon longifolium the largest among the local Acaulon species is characterized by the long entire leaves not or hardly concealing the mature capsule, long excurrent costa with large somewhat inflated ventral cells. A table comparing the new species with closely related ones is added. The main diagnostic character of Pottia gemmifera is its bud shaped propagula in at least some leaf axils. Barbula ehrenbergii var. gemmipara differs from the typical variety by the abundant multicellular fusiform axillary gemmae.

Breeding experiments were carried out inCalendula species. In the annuals, which are selfers, rarely some outcrossing was observed only in the most peripheral flowers. In experimental crosses fruit was produced in all combinations. Fertile F1 and F2 hybrids could be grown from crosses between parents with similar chromosome numbers:C. palaestina ×C. pachysperma and crosses of different morphological forms ofC. arvensis. In crosses of species with different chromosome numbers at least partly fertile F1 hybrids were obtained fromC. tripterocarpa ×C. stellata andC. tripterocarpa ×C. arvensis and crosses of the latter withC. palaestina. Fertile F2 plants were grown from the combination ofC. arvensis ×C. tripterocarpa. Considering this information and previously obtained data, a scheme is proposed for explaining speciation in the genusCalendula.

Components of the total sexual investment of plants growing under mediterranean climatic and edaphic conditions were compared with those of plants growing in the desert, in the closely related allogamous species pair Erucaria hispanica and E. rostrata and in populations of the autogamous species Erophila minima. In all cases lower total investment was evident in the desert plants. At the prezygotic phase it was expressed by (1) reduced production of flowers; (2) lower allocation to the production of male gametophytes and some floral organs; and (3) packaging of more ovules per ovary. The ratio of reproductive: vegetative biomass which was found to be greater in the desert plants and their lower pollen: ovule ratio are perhaps indicative of greater efficiency. Their smaller investment at the postzygotic phase was expressed in: (1) reduction in total numbers of fruits and seeds; (2) decrease in seed size and weight. Yet in the desert plants the number of seeds per total biomass was found to be significantly larger and fertility rates (seed-set per ovule, fruit-set per flower per plant) were equal to or greater than those in the mediterranean plants. The trends observed in this study in desert plants, which may result in more efficient exploitation of resources, are similar in the species involved, regardless of their breeding system-autogamous or allogamous.

The generic name MedicagoL. should by typified by M. radiataL. and not by M. sativaL. Acceptance of specimens in the Linnaean herbarium as types of certain Medicagospecies should not be ‘automatic’ but based on an analysis of each particular case showing that the specimen in question is indeed in accordance with the protologue and not a later addition to the herbarium.