Temperature-dependent dry receptor on antenna ofPeriplaneta. Tonic response

Summary Identified as a dry receptive unit by transitory impulse frequencies up to about 200 imp/sec during rapid drops in humidity (Fig. 3) and which no other modality elicited, the dry unit on the antenna ofPeriplaneta americana is characterized by a regular (Fig. 4) and relatively high stationary impulse frequency (10–65 imp/s). Without exception the stationary discharge rate (tonic frequency) rose with falling values of stationary absolute humidity at constant temperature, and with rising values of stationary temperature of ambient air at constant humidity. Enthalpy and evaporation cooling appear to be ruled out as exclusive adequate explanations for this double dependence. No matter whether tonic frequency is plotted against absolute humidity based on either volume of moist air or weight of dry air, or against partial pressure of water vapor in ambient air, or the difference between saturation and partial vapor pressure, or against relative humidity, the dependence on the temperature is not eliminated (Figs. 5–7). Because a temperature range of about 20 °C and all humidities between 0 and 100% occupy the same large segment of the unit's tonic frequency spectrum (Fig. 8), the unit is termed bimodal.The author wishes to express indebtedness and gratitude to Prof. Dr. Hansjochem Autrum for backing the early stages of this project with the assistance of the Deutsche Forschungsgemeinschaft, to Prof. Dr. Helmut Altner for his prolonged support, to Dr. Hans-Jürgen Hinz for his helpful discussion of questions involving thermodynamics, to Prof. Dr. Friedrich Earth for helpful criticism of the text, and to Miss Christel Praeg for tireless technical assistance.     

Hygroreceptor identification and response characteristics in the stick insectCarausius morosus

Summary Simultaneous recordings were made from 3 sensory units in an easily identifiable sensillum on the 12th antennal segment ofCarausius morosus. Impulse frequency (F) of one unit rose sharply when either the temperature (T) or the partial pressure of water vapor (Pw) was suddenly lowered. F of another rose sharply either when T was suddenly lowered or Pw was raised. F of the third was hardly affected by sudden changes in T but rose abruptly when Pw fell (Fig. 1). The reactions of the first may be explained by enthalpic cooling and is considered a cold cell. Those of the second may be attributed to changes in relative humidity (Hr) and is thus termed a moist cell. The third is taken to be the latter's antagonist, a dry cell.A 90%-probability that a single moist cell of average differential sensitivity will correctly discriminate between two humidity levels is not reached until the difference between the two is 38% Hr. The dry cell requires a difference of only 7.5% (Table 1). The basis for discrimination is a single presentation of each level.The power to discriminate Hr steps is better in both cell types. For a single moist cell of average differential sensitivity the difference required between the steps for a 90%-probability of correct discrimination is only 6.3% Hr; for the dry cell, 3.5% Hr. Basis for discrimination: a single presentation of each step. Step range: 5% to 55% Hr.Abbreviations F impulse frequency in impulses per second (imp/s) - Hr orHR relative humidity in % - Ps saturation pressure of water vapor in torr - Pw partial pressure of water vapor in torr - r correlation coefficient - T temperature in °C Dedicated to Prof. Dr. F. Schaller on the occasion of his 65th birthday     

Antennal hygroreceptors of the honey bee,Apis mellifera L.

Summary Antennal hygroreceptors of the honey bee, Apis mellifera L., have been investigated electrophysiologically and the sensillum containing these receptors with SEM. Moist and dry hygroreceptors have been identified along with a thermal receptor in a specialized coeloconic sensillum. This sensillum comprises a cuticular, shallow depression (diameter; 4 ) having a central opening (1.4–1.5 m) and a mushroom-shaped protrusion (1.4–1.5 m) from the opening. The head of the protrusion is irregular in shape and is not perforated. This sensillum has been thus far referred to as a sensillum campaniformium (Dietz and Humphreys 1971), henceforth, it is referred to as a coelocapitular sensillum.The responses of both moist and dry hygroreceptors are of a phasic-tonic manner. Both receptors are antagonistic with respect to their responses to humidity; one responds with an increase in impulse frequency to rising humidity, the other to falling humidity. The humidity-response relationship is independent of stimulus flux.     

Antennal warm and cold receptors of the cave beetle,Speophyes lucidulus delar., in sensilla with a lamellated dendrite

Summary Electrophysiological examination of the 2 black-hair sensilla on the antennae of both larval stages of the cave beetle,Speophyes lucidulus, has revealed in each a pair of antagonistic thermal receptors (Fig. 1). Each sensillum was known to house the dendrites of 2 sensory cells which are associated with the extensively lamellated dendrite of a third (Corbière-Tichané 1971). One unit, a cold receptor, responds to temperature drops of 1 to 7 °C from initial temperatures between 9 and 14 °C with impulse frequencies up to 200 imp/s (Figs. 3, 4). Its antagonist, encountered less than 10% as often, is a warm receptor which responds with similar impulse frequencies to rapid rises in temperature from the same 9–14 °C (Figs. 3, 6). As indicated by the average gain of 24 imp/s for an increase of 1 °C in temperature drop, the cold unit appears almost twice as sensitive to sudden temperature change as the warm unit (14 (imp/s) °C). Examination of response scatter indicates that the average cold unit should on the basis of a single pair of responses be able to designate the greater of two temperature drops between 1 and 7 °C with 90% probability when they differ by 0.7 °C (Fig. 5). Though not yet definitive, evidence is accumulating that the third physiological unit is a dry air receptor.Abbreviations F impulse frequency in imp/s - Fc F as calculated - Fm F as measured - imp impulses - Pw partial pressure of water vapor in air - Ps saturation pressure of water vapor - r regression coefficient - T temperature - difference in Supported by the Deutsche Forschungsgemeinschaft, Sonder forschungsbereich 4, Projekt DThe authors wish to express their indebtedness to Dr. Renate Beinhauer, Faculty of Natural Sciences I — Mathematics, Univ. of Regensburg, for her help in applying statistical methods in determining resolving power.     

Response of moist-air receptor on antenna of the stick insect,Carausius morosus,to step changes in temperature

Summary The moist-air sensory cell in the antennal mound-shaped sensillum of Carausius responds to changes in relative humidity brought about by changing either the temperature (T) of the air or the partial pressure of water vapor (Pw) (Figs. 1, 5). When changes in either parameter cause relative humidity (Hr) to rise between roughly 5% and 55%, the same Hr-changes elicit very close to the same responses, no matter how Hr is changed (Figs. 2, 3). Even the resolving power for upward Hr-steps produced by lowering T is very close to that produced by raising Pw: 7.4% vs. 6.3%. Thus upward transients in impulse frequency (F) may be read off directly as quantitative rises in Hr. Whether the rise in Hr as signalled by the moist-air cell is the result of a rise in Pw or of a drop in T could well be indicated by the simultaneous reactions of the cold and dry-air cells (Figs. 1, 5). The moist-air cell also reacts to downward step changes in Hr, but very differently, depending on how they are brought about. Upward steps in T have a much larger effect on F than corresponding downward steps in Pw (Fig. 4). This result demonstrates that changes in relative humidity do not suffice to explain the changes in the activity of the moist-air cell. The receptor may be better construed as bimodal, reacting to changes in T and Pw with independent sensitivities and well matched to relative humidity when changes in either lead to increases in this parameter. The moistair cell's responses to T-steps at Pw = 0 (Figs. 1, 5) offer some support for this interpretation.Abbreviations F impulse frequency in impulses/s (imp/s) - Hr relative humidity in % - Ps saturation pressure of water vapor in torr - Pw partial pressure of water vapor in torr - r correlation coefficient - T temperature in °C     

蜚蠊单个棘—钟形感器冲动发放的特性

本文分析了蜚镰后胸足单个棘一钟形感器对机械位移刺激的反应模式以及冲动发放的特性.结果证明该感器是一种适应较慢的相位性触觉感受器,对触刺激有相当稳定的反应.     

Comparative study on the responses of maxillary sensilla styloconica of cotton bollwormHelicoverpa armigera and Oriental tobacco budwormH. assulta larvae to phytochemicals

Using the electro-physiological technique, the sensory mechanisms of maxillary sensilla styloconica to stimulants and deterrents were explored on two closely related species, the generalistHelicoverpa armigera and the specialistH. assulta. The results showed that: (i) in both species, cells sensitive to sucrose and azadirachtin were mainly in the lateral sensillum styloconicum, and those to inositol were in the medial sensillum styloconicum; (ii) sensitivity of medial sensillum styloconicum inH. assulta to inositol was higher than that inH. armigera; (iii) among 6 tested deterrents, only azadirachtin evoked high impulse discharge from the lateral sensillum styloconicum in both insects; (iv) the deterrents could disturb stimulants evoking impulse discharge from maxillary sensilla styloconica of both species in different degrees: To sucrose evoking impulses on lateral sensillum styloconicum, forH. armigera capsaicin had a strong inhibition and gossypol had a weak inhibition, while forH. assulta tannic acid, gossypol, and tomatine all had strong inhibition except nicotine and capsaicin; to inositol evoking impulses on medial sensilum styloconicum, forH. armigera inhibition of tomatine was strong but that of gossypol was weak; and forH. assulta inhibition of gossypol was strong but that of nicotine was weak.     

Electrophysiological evidence of synaptic interactions within chemosensory sensilla of scorpion pectines

The pectines of scorpions are ventral bilateral appendages supporting 10⁴–10⁵ chemosensory sensilla called pegs. Each peg contains 10–18 sensory neurons, some of which show ultrastructural evidence of axo-axonic synapses with other sensory neurons in the same sensillum. In extracellular recordings from single-peg sensilla, individual sensory units can be distinguished by impulse waveform and firing frequency. Cross-correlation analysis of impulse activity showed that at least two of these units, types `A1' and `A2', are inhibited during the 100-ms period immediately following activity of a third unit, type `B'. This interaction between sensory units in a single sensillum also occurs in surgically isolated pectines, indicating that it does not involve efferent feedback from the central nervous system. Other sensillar neurons appear to have excitatory interactions. Thus, in scorpion pectine, chemosensory information undergoes some form of processing within individual sensilla prior to its relay to the CNS, making this an unusually accessible preparation for study of first-order chemosensory processing events. Accepted: 12 April 1997     

Midday stomatal closure in Mediterranean type sclerophylls under simulated habitat conditions in an environmental chamber

Summary Shrubs of the Mediterranean sclerophyllous species Arbutus unedo and Quercus ilex were studied under simulated habitat conditions in an environmental chamber. Temperature, humidity, and light intensity were altered stepwise to simulate diurnal changes in conditions similar to those measured in an evergreen macchia in Sobreda, Portugal. Leaves were enclosed in cuvettes which reproduced the growth chamber climate and which allowed measurement of gas exchange. Increasing atmospheric stress in the form of higher temperature and lower humidity on successive days gradually results in midday depression of transpiration rate and net photosynthesis rate of leaves due to midday stomatal closure.Dedicated with the greatest appreciation to a scientist, Prof. Dr. M. Evenari, who has stimulated ecological work all over the world and to a publisher, Dr. F.K. Springer, who has promoted communication among scientists and distributed results of their experimentation worldwide     

Die Fagus-Sippen Europas und ihre geographisch-soziologische Korrelation zur Verbreitung der Assoziationen des Fagion s.l.

Studies of the beeches and beech woods of eastern central Europe revealed, that in the postglacial period not only Fagus sylvatica (L.) emend. reimmigrated from the refugial territories in the SE-as has generally been accepted, but also the transitional taxa, which originated from hybrids with F. orientalis Lipsky. The NW area limit of these intermediate taxa must be revised. The presence in central Europe of these taxa-which form own Fagion alliances and associations in the SE (Fagus intermedia ssp. moesiaca and ssp. taurica) as well as the presence of other southeastern species in central European beach woods shows, that their postglacial development is parallel to, but different from other areas. The taxon Fagus intermedia (ssp. neglecta and ssp. transitus) became differential taxa of a central European region of the Fagion medioeuropaeum. Plant sociologists are therefore requested to make new and critical analyses of the beech woods in Europe, with special attention to the Fagus taxa, in order to establish in detail the geographical distribution and phytosociological significance of Fagus intermedia.The author offers to determine or revise Fagus material (herbarium collections).

Danksagung. Ich möchte meinen tiefsten und allzeitigen Dank besonders den Herren Prof. Dr. A. O. Horvat (Pécs), Prof. Dr. Ch. Moulopoulos, Prof. Dr. B. Jovanovié, Prof. Dr. I. Dumitriu-Tataranu, Prof. Dr. R. Bornkamm, Prof. Dr. M. A. Kotschkin, Prof. Dr. P. Fukarek, Prof. Dr. K. Browicz für gewährte Unterstützung aussprechen und ganz besonders unserem unvergeßlichen verstorbenen Prof. Dr. Drs. h.c. R. Tüxen, der mir zur Fortführung dieser Studien Mut machte.     

Analysis of the electrical responses of antennal thermo- and hygroreceptors of Antheraea (Saturniidae,Lepidoptera) to thermal,mechanical, and electrical stimuli

Summary Antennal styloconic thermo-hygro sensilla of Antheraea were studied with DC-coupled transepithelial recordings. — The transepithelial voltage changed by about 2 mV · °C^–1. The spike frequency of the cold cell reached 300 Hz at the onset of negative temperature steps, but only 30 Hz at static temperatures (as with metal electrodes). The cold cell spikes showed a brief afterhyperpolarization that increased with temperature. The spikes of the cold- and warm-stimulated cells facilitated each other at low temperature. Mechanical stimuli (push against the sensillum, hydrostatic pressure of < ± 50 kPa, ultrasonic vibrations 120 kHz) modified the responses of the cold- and the warm-stimulated cells. Latency of cold cell responses to ultrasonic stimulation was occasionally less than 3 ms. — The impulse frequencies of the warm and the cold cells depend on the temperature and the magnitude of temperature change. When the firing rate is high enough by either or both of these parameters, it can be forced still higher by application of clamp current (outside positive). The higher the firing rate prior to clamping, the greater the effect of the current. — By analogy with sensilla for other modalities, this relationship between frequency and clamp current strongly suggests that stimulus-dependent changes in the conductance of dendritic membranes control the excitation of the warm and cold cells.Abbreviations DC direct voltage - TER transepithelial slope resistance between recording electrode and reference electrode in the hemolymph - NTC thermistor with negative temperature coefficient - TEV transepithelial voltage between electrodes - THS thermo-hygro sensillum     

Comparative study on the responses of maxillary sensilla styloconica of cotton bollwormHelicoverpa armigera and Oriental tobacco budwormH. assulta larvae to phytochemicals

Using the electro-physiological technique, the sensory mechanisms of maxillary sensilla styloconica to stimulants and deterrents were explored on two closely related species, the generalist Helicoverpa armigera and the specialist H. assulta. The results showed that: (i) in both species, cells sensitive to sucrose and azadirachtin were mainly in the lateral sensillum styloconicum, and those to inositol were in the medial sensillum styloconicum; (ii) sensitivity of medial sensillum styloconicum in H. assulta to inositol was higher than that in H. armigera; (iii) among 6 tested deterrents, only azadirachtin evoked high impulse discharge from the lateral sensillum styloconicum in both insects; (iv) the deterrents could disturb stimulants evoking impulse discharge from maxillary sensilla styloconica of both species in different degrees: To sucrose evoking impulses on lateral sensillum styloconicum, for H. armigera capsaicin had a strong inhibition and gossypol had a weak inhibition, while for H. assulta tann     

The ultrastructure of campaniform sensilla on the eye of the cricket,Gryllus campestris

Summary The structure of the campaniform sensilla of the cricket eye was investigated by light and electron microscopy. Each sensillum is innervated by a single bipolar neuron. Its axon extends through the retina into a side-branch of the nervus tegumentarius. The dendrite extends through a cuticular channel to the surface of the cornea. The distal part of the dendrite, the sensory process, contains a tubular body and is attached to a cuticular cap which is obliquely inserted into the exocuticle between the corneal lenslets. Some particular structural features as well as the function of the campaniform sensillum of the cricket eye are discussed.Supported by the Deutsche Forschungsgemeinschaft, grant Ho 463/10The authors are indebted to Prof. H. Altner, University of Regensburg, and Mrs. Evelyn Thury, Contron GmbH, München for use of the scanning electron microscope facilities     

Proprioceptive feedback in locust kicking and jumping during maturation

Campaniform sensilla monitor the forces generated by the leg muscles during the co-contraction phase of locust (Schistocerca gregaria) kicking and jumping and re-excite the fast extensor (FETi) and flexor tibiae motor neurones, which innervate the leg muscles. Sensory signals from a campaniform sensillum on the proximal tibia were compared in newly moulted locusts, which do not kick and jump, and mature locusts which readily kick and jump. The activity pattern of FETi during co-contraction was mimicked by stimulating the extensor tibiae muscle. Less force was generated and the spike frequency of the sensory neurone from the sensillum was significantly lower in newly moulted compared to mature locusts. Depolarisation of both FETi and flexor motor neurones as a result of sensory feedback was consequently less in newly moulted than in mature locusts. The difference in the depolarisation was greater than the decrease in the afferent spike frequency suggesting that the central connections of the afferents are modulated. The depolarisation could generate spikes in FETi and maintain flexor spikes in mature but not in newly moulted locusts. This indicates that feedback from the anterior campaniform sensillum comprises a significant component of the drive to both FETi and flexor activity during co-contraction in mature animals and that the changes in this feedback contribute to the developmental change in behaviour.Abbreviations aCS anterior campaniform sensillum - ETi extensor tibiae - FETi fast extensor tibiae motor neurone - FlTi flexor tibiae - pCS posterior campaniform sensillum     

Experimental analysis of the prey catching behavior ofHydromantes italicus Dunn (Amphibia,Plethodontidae)

Summary 1. The Italian bolitoglossine salamanderHydromantes italicus shows a periodic cave life. In spring and in the fall it leaves the caves after which it lives under stones, in leaves and crevices. Inside the limestone caves,H. i. can be found both in the zone of dim light near the entrance and in total darkness. 2. Corresponding to these two environments there are two guidance systems of the prey catching behavior: one visual and one olfactory. 3. The visually guided prey catching behavior is determined by the stimulus parameters: velocity, size, contrast, and ambient illumination. Continuously moving objects are effective within a velocity range of 0.05 to 6 cm/s with an optimum at 1.25 cm/s (Fig. 2). Stimuli moving stepwise elicit fixation of the prey and complete approach more frequently than continuously moving stimuli. The prey size which elicits prey catching ranges from 0.5 to 10 mm² with an optimum size between 2.5–5.0 mm² (Fig. 3). The prey catching behavior is hardly impaired by a decrease in ambient illumination down to 0.03 cd/m². Beyond 0.03 cd/m², the prey catching activity decreases sharply, but there are still responses at an illumination level of 0.003 cd/m² (Fig. 4). 4.H.i. also responds to stationary non-smelling visual stimuli following stimulation by smell or movement.H.i. is able to detect prey by smell only both in total darkness and in the light (Fig. 5 A). In the light, the prey catching behavior with regard to smelling objects is inhibited by the absence of visual contrast (Fig. 5B).I would like to thank Prof. Dr. R. Altevogt, University of Münster (Germany) for his generous help and constant encouragement. Furthermore, I want to express my gratitude to Prof. Dr. D.B. Wake, University of California, Berkeley (USA), Prof. Dr. P. Mancino, University of Pisa (Italy), and Prof. Dr. J.-P. Ewert, University (GH) of Kassel (Germany) for stimulating discussions and helpful comments.     

Microspectrofluorometric identification of formaldehyde induced fluorescence in hypothalamic nuclei of Xenopus laevis tadpoles

Summary To identify the monoamine (s) produced in the paraventricular organ (PVO) and the nucleus infundibularis dorsalis (NID) of Xenopus laevis tadpoles, formaldehyde-induced fluorescence in these hypothalamic structures was analysed by microspectrofluorometric techniques. Reference values were obtained by recording excitation and emission spectra of fluorescence in monoamine containing protein models. The maxima of the excitation and emission spectra, both under normal conditions and after treatment with HCl vapour, indicate the presence of dopamine. Based on a number of emission spectra, the PVO and NID might also contain serotonin. With regard to the functional significance of dopamine produced in the hypothalamic nuclei, it may be concluded that the catecholamine is probably identical with the melanotropin inhibiting factor (MIF).The authors wish to thank Prof. Dr. P.G.W.J. van Oordt for his stimulating interest and support. The skillful assistance and valuable contributions of Miss A. G. Fennema and Miss M.G.A. de Bruyn are gratefully acknowledged. Many thanks are due to Prof. Dr. A. Oksche for the opportunity of performing measurements on fluorescence, during a visit to his institute (Zentrum für Anatomie und Cytobiologie, Gießen, BRD). The measurements were carried out by Dr. H.-G. Hartwig, whose help and advice are highly appreciated.     

Secondary sensory cells in the gravity receptor system of the statocyst of Octopus vulgaris

Summary The presence of secondary sensory cells in the Octopus gravity receptor system has been demonstrated. In serial thin sections of the receptor cells (hair cells) no axons were found leaving the cells. Instead, synapses were observed with synaptic vesicles lying inside the receptor cells. Both data clearly indicate that the receptor hair cells represent secondary sensory cells. In addition, efferent contacts to the receptor cells could be confirmed.This work was supported in part by grant Wo 160/5 of the Deutsche Forschungsgemeinschaft to Prof. Dr. H.G. WolffThe experimental work was done in part at the Zoological Station in Naples and at the Sechenov Institute of Evolutionary Physiology and Biochemistry of the USSR Academy of Sciences (Laboratory of Prof. Dr. Ya.A. Vinnikov), Leningrad, USSR. The authors thank Prof. Vinnikov and Dr. Tsirulis for stimulating discussions     

Diversity models applied to a chalk grassland

In a permanent plot experiment started in 1971, the effects of several management regimes on diversity of a Dutch chalk grassland have been investigated and the results have been compared to existing models predicting general trends in diversity. Treatments included grazing, mowing, and leaving untouched; in the mown plots, the effects of fertilizing and sod cutting were also studied. Grazing resulted in the highest diversity, leaving untouched in the lowest (ca. 42 and 15 spp. per m², respectively). Within the mown plots, fertilizing decreased diversity. The effects of sod cutting disappeared after some years. The results conform best with the response surface model of Huston (1979) relating diversity to frequency of population reduction and rate of competitive displacement, but a slight modification of the shape of the surface is suggested.Nomenclature follows van der Meijden et al., 1983.The authors are very grateful to Dr J. Miles (Banchory, U.K.) for stimulating remarks and to Prof. Dr. M. J. A. Werger, Dr R. K. Peet and two reviewers for many valuable comments and suggestions.     

CO2-Fixierungsreaktionen bei der Salzpflanze Mesembryanthemum crystallinum unter variierten Außenbedingungen

Summary The correlation of CO₂-fixation metabolism to various environmental conditions such as NaCl content of culture medium, air humidity and light intensity was investigated in the halophytic species Mesembryanthemum crystallinum. The data obtained demonstrate that a change in photosynthesis from C₃-pathway to crassulacean acid metabolism (CAM) is observed not only in NaCl treated plants as reported earlier but also in control plants grown in non-saline medium when environmental conditions (high light intensity, low air humidity) cause a water deficit in the leaves. It is suggested that water stress plays an important role in regulation between C₃- and CAM-pathway of photosynthesis in Mesembryanthemum crystallinum.

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Abkürzungen CAM Crassulaceensäurestoffwechsel - FG Frischgewicht - TG Trockengewicht - D Ende Dunkelphase - L Ende Lichtphase Herrn Prof. Dr. Otto Stocker zum 85. Geburtstag gewidmet     

Die Inhaltsstoffe einigerPertusaria-Arten mit C+ rot reagierendem Thallus (Lichenes,Pertusariaceae)

Zusammenfassung 67 Proben von 5Pertusaria-Arten, deren Thallus C+ rot Reaktion zeigt, wurden dünnschicht- und papierchromatographisch geprüft.P. hemisphaerica undP. velata (beide mit Lecanorsäure) sowieP. bryontha undP. subviridis (beide mit Gyrophorsäure) wurden erstmals chemisch untersucht. InP. lactea wurde das Vorkommen von Lecanorsäure und Variolarsäure bestätigt. 2 Proben, die nur alsP. lactea bestimmt werden können, jedoch dem Typ nicht entsprechen, enthielten zusätzlich Spuren Psoromsäure. Weiterhin wurden 5 Proben vonP. rupestris (C-)geprüft (mit Stictinsäure und dem Xanthon Coronaton).Beide Autoren: 1 Berlin 41, Grunewaldstr. 35.Für die Entleihung von Herbarmaterial danken wir den Herren Prof. Dr. G.Follmann (B), Prof. Dr. H.Merxmüllee (M), Prof. Dr. J.Poelt (Berlin) und Dipl.-Ing. H.Ullrich (Goslar), für die Überprüfung einiger Proben Herrn Dr. O.Almborn (Lund). Für die Überlassung von Testsubstanzen sind wir den Herren Prof. Dr. G.Follmann (B), Dr. habil. S.Huneck (Freital) und Frau Dr. C. F.Culberson (Durham, N. C.) zu Dank verpflichtet. — Herrn Prof. Dr. J.Poelt danken wir sehr für die Anregung der Arbeit und die ständige Beratung bei der Durchführung.