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The use of machine tools in flexible automation increases the requirements on spindle drives in terms of reliability and availability. Today the DC-drive with speed control is a standard solution. Brushless drives are the state of the art in servo applications. Frequency controlled asynchronous machines supplied by transistor inverters are beginning to enter the area of brushless spindle drives. Urged by the demands of high reliability, ease of servicing, simple installing, high speed and a wide range of constant power to economize gear trains, several producers offer AC spindle drives to replace the DC drives. To get the same control behaviour it is necessary to use a sophisticated control algorithm which can be handled by a microcomputer much better than by analogue circuits. This paper demonstrates the realization of an AC spindle drive with microcomputer control. The price of this product is nearly as low as the price of comparable DC drives.

The closely related Scrophulariaspecies of the Middle European flora S. auriculata, S. umbrosaand S. nodosaare remarkably different as to the distribution patterns and growth forms. Chorological and morphological studies show distinct differences in the general distribution (especially with regard to the zonal and to the oceanic-continental climatical conditions) and the vegetative characters. The westmediterranean-atlantic S. auriculatashows the least specialisation of ramification, innovation, radication, sequence of leaves and seasonal rhythm. On the other side, the species with the northernmost distribution, S. nodosa, is most advanced. The comparative study of growth forms demonstrates within the S. scorodonia-group a progression of taxa from vigorous evergreen semishrubs (in the Canaries and in the South-Western-Mediterraneis) to ever-wintergreen chamaephytical herbaceous perennials (in the oceanic parts of Southern and Middle Europe) to wintergreen hemicryptophytes (in the suboceanic-subcontinental parts of Southern and Middle Europe) and to summergreen geophytes (in Middle and Northern Europe). Probably in this series we may recognize a model of the evolution of temperate forest plants from a subtropical-meridional tertiary vegetation. The authors propose to use correlated studies of distribution patterns and growth forms as a base of ecotaxonomical research and as a material for Biological Floras.

The aim of this study was to investigate the ecophysiological differentiation between two closely related plant species with different distribution. The areas of Carlina vulgarisa South-Central-European, and C. biebersteiniian East-European-Middle-Siberian element overlap in Central Europe, where both species could be studied in the field and in a transplant garden. Dry matter partitioning and vertical leaf area distribution are similar in both species. However, leaf structure, stomatal behaviour, rooting pattern and organ temperatures differ significantly. In C. biebersteiniileaves are more mesomorph, stomata are more sensitive to dry air and root length per unit leaf area is much smaller than in C. vulgaris. Under radiation conditions leaf and flower temperatures in C. biebersteiniiare higher than in C. vulgaris. Changes in leaf sequence are more pronounced in C. biebersteinii. Thus, C. biebersteiniishows features that appear adequate for moderate light and high humidity conditions in dense herbaceous plant canopies, whereas C. vulgarisis a typical heliophytic forb of open habitats. This corresponds with the different natural growth conditions of the two species: C. biebersteiniigrows in relatively dense canopies under conditions of a short but prevailingly humid growing season (East-European-Siberian forest step) whereas C. vulgarisis found in open pioneer habitats with periods of water-stress during a much longer growing season (Submediterranean-Central-European areas). Finally we discuss the ecological significance of the large leaf area accumulation on the flowering heads of both species with respect to gas exchange.

The most important forest communities of the West-Himalayas, in the older literature hitherto characterized only as to the combination of their tree species, are thoroughly described and represented by complete species lists and an analysis of the chorological spectrum. Special attention is paid to the sclerophyllous forests of Quercus balootand Olea ferrugineaand to the Cedrus deodaraforests growing in mediterranoid climats. The relations of these Himalayan communities to Mediterranean forest associations are discussed. In the same manner the corresponding structure and ecology of the Pinetum roxburghii and the Pinetum canariensis are elucidated.