The high velocity, large drift, and high humidity in the air scrubber may have contributed to the wide spread of Legionella species, probably for >10 km. The risk of Legionella spread from air scrubbers should be assessed.

Our results indicate that S. pneumoniae is the most common bacterial cause of pneumonia in hospitalized patients, and the prevalence of Legionella pneumonia is probably higher in Norway than recognized previously.

SIMONSEN, 0. 1975. Cytogenetic investigations in diploid and autotetraploid populations of Festuca pratensis. -Hereditas 79: 73-108. Lund, Sweden. ISSN 0018-0661. Received July 26, 1974 Cytogenetic investigations were conducted in diploid and induced autotetraploid population plants of a local Norwegian variety of Festuca pratensis, HUDS. Meiotic investigation in 50randomly selected diploid genotypes revealed that 42 % of the clones were heterozygous for paracentric inversions and 22 % for interchanges. In the autotetraploid C2-generation, 73 % of the clones had normal euploid chromosome number (2n= 28). Among the remaining aneuploid clones the chromosome number ranged from 26 to 30, 2n= 27 and 2n= 29 being the most common. At first metaphase quadrivalents were regularly formed, the mean number among euploid clones ranging from 1.73 to 3.33. The corresponding variation in the mean number of chiasmata was from 22.67 to 26.33. Generally, the quadrivalents disjoined regularly at first anaphase, and the major causes of aneuploid gametes were univalents and trivalents. The mean percentage of normal pollen grains and seed set was significantly higher in the eutetraploid clones than in the diploids. The aneuploid classes with 27 and 29 chromosomes had significantly lower fertility than the eutetraploid class. Between the aneuploid classes no significant difference appeared, but the figures indicate a more serious effect upon fertility of one missing than of one extra chromosome. The yielding capacity of diploids exceeded that of eutetraploids by 7 %, and the difference was highly significant. An even geater difference appeared between eutetraploids and aneuploids. Between the two aneuploid classes with 27 and 29 chromosomes, however, no significant difference could he detected.

The meiotic properties were studied in two Norwegian populations of Phleum pratense L. (Grindstad and Bodin), one Danish (Pajbjerg) and one Russian population (Rjadovaja). At diakinesis, multivalents in addition to bivalents were found in most of the sporocytes examined, and the mean frequency per sporocyte ranged from 1.09 in Bodin to 1.39 in Grindstad. The differences between populations were not statistically significant. First metaphase was unsuitable for determination of bivalents and multivalents because the chromosomes were clumped together on the equatorial plate. The frequency of MI's with univalents could, however, be determined with certainty, and the average per cent of cells with univalents was 8.7 in Rjadovaja, 18.4 in Pajbjerg, 20.9 in Grindstad and 33.1 in Bodin. Comparisons between the 4 populations showed that Rjadovaja had a significantly lower frequency of MI's with univalents than the others. The remaining populations, on the other hand, did not differ significantly, though the frequency of sporocytes with irregularities at MI and later stages generally was higher in Bodin than in Grindstad and Pajbjerg. The mean frequency of multivalents at diakinesis and first metaphase with univalents varied continuously among plants within populations, and the variation was of the same kind as that found for characters like earliness, plant height etc. Unpaired chromosomes at MI were the most common reason for irregularities at later stages of meiosis and in tetrads, whereas multivalents seemed to play a relatively minor role.

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