Chromosome numbers in Nigerian Compositae

Chromosome counts are presented for 54 collections of Nigerian Compositae. The collections comprise 37 taxa belonging to 21 genera and 34 specieS. Most of the taxa studied are colonisers of disturbed habitats.     

Chromosome numbers in Malawian Commelinaceae

In this account chromosome numbers of 22 species and varieties from five genera of Commelinaceae occurring in Malawi are given. For 14 of them this is the first time their chromosome numbers have been reported. A wide range of chromosome numbers of 2n = 26 , 28, 30. 44. 52 and 60 is noted in Commelina.     

Chromosome numbers of the genusCalamagrostis in Japan

Chromosome counts for 783 collection ofCalamagrostis in Japan are reported. These include the first record forC. tashiroi and the reports of new cytotypes inC. stricta, C. hakonensis andC. longiseta. The geographical distribution of different cytotypes ofC. langsdorffii andC. hakonensis is outlined. Counts are also reported for a number of “intermediates” which are supposed to be interspecific hybrids or hybrid derivatives. A summary of chromosome counts for JapaneseCalamagrostis so far recorded is tabulated. No diploid plants with 2n=14 chromosomes are found. The tetraploid taxa, which are plentiful and seem to have adaptively radiated in Japan, jack any sign suggestive of their recent origin from the diploids. It is suggested that plant with 2n=28 (4X in the traditional sense) may be regarded as semidiploid and having that behavior, and that speciation ofCalamagrostis in Japan has occurred principally at this chromosome level. Speciation by means of amphiploidy may have been scarce. It is also suggested that hybridization and polyploidy have greatly contributed to the formation of complicated internal structure of various species.     

Chromosome numbers of the European seagrasses

The chromosome numbers of the five European seagrasses have been determined in material from several sites along the coasts of the Atlantic Ocean, the North Sea and the Mediterranean:Zostera marina L., 2n = 12;Z. noltii Hornem., 2n = 12;Posidonia oceanica (L.)Delile, 2n = 20;Cymodocea nodosa (Ucria)Aschers., 2n = 14, 2n = 28;Halophila stipulacea (Forsk.)Aschers., 2n = 18. The difference in chromosome morphology betweenZ. marina andZ. noltii supports the division of the genus into two subgenera.     

Chromosome numbers of the Australian Zosteraceae

 Somatic chromosome numbers of 2n = 24 are reported for all three species of Australian Zostera: Z. capricorni Aschers., Z. muelleri Irmisch ex Aschers. and Z. mucronata den Hartog and 2n = 36 for Heterozostera tasmanica (Martens ex Aschers.) den Hartog. All Australian zosteroidean species apparently have similar chromosome morphology: dot-like or rod shaped. It is suggested that the chromosome number and its morphology can be used to distinguish genera and subgenera in the Zosteraceae but not for species identification, and that speciation is not accompanied by changes of chromosome numbers. Received December 1, 1999 Accepted September 6, 2000     

Chromosome numbers of the Australian Cymodoceaceae

The somatic chromosome numbers of the eleven Australian seagrass species belonging to five genera in the Family Cymodoceaceae were determined. The chromosome numbers in Amphibolis and Thalassodendron are reported for the first time. Cymodocea and Halodule species have the following chromosome numbers: Cymodocea angustata Ostenf., 2n = 14, 28; C. rotundata Ehrenb. & Hempr. ex Asch., 2n = 14; C. serrulata (R. Br.) Asch. & Magnus, 2n = 14, 28; Halodule pinifolia (Miki) den Hartog, 2n = 32; H. uninervis (Forsk.) Asch., 2n = 32; H. tridentata (Steinh.) Endl. ex Unger, 2n = 14. Halodule has the highest chromosome numbers among the seagrasses and they are the largest in sizes with a distinct bimodal type in the family. Syringodium isoetifolium (Asch.) Dandy has 2n = 20. Both endemic Amphibolis antarctica (Labill.) Sonder ex Asch. and A. griffithii (J. Black) den Hartog have 2n = ca. 36 and have the smallest chromosomes in the family appearing as small dots. Thalassodendron pachyrhizum den Hartog has 2n = 28. Chromosome numbers appear to be identical or closely related among different species in the same genus but they vary in the five genera in the Cymodoceaceae suggesting that these five genera may have evolved independently in the past.     

Chromosome numbers in Impatiens from Thailand

Chromosome numbers are given for Impatiens chiangdaoensis (2n = 12), I. violaeflora (2n = 10, 12) and I. mengtzeana (2n = 16). A survey of known chromosome numbers of Impatiens from Thailand is also given.     

Chromosome numbers in some pear cultivars

V sortimentu hru?ni d?le?itěj?ích pro pěstování v ?eskoslovensku nebyl dosud znám po?et chromosom? u 11 sort. Bylo proto provedeno toto zji?tění a shledáno, ?e v?echny tyto sorty jsou diploidní, 2n=34. Jsou to: Ananaska ?eská, Anglická bergamotka, Bezjaderka ?íhova, ?istecká banánová, Fulvie, Jeanne d'Arc, Kolmarská zlatá, Monchallardova, Notá? Lepin, Sterkmansova máslovka a Zefyrinka. Provedeno té? ově?ení star?ích údaj? o diploidním stavu sort Kongresovka a Olivier de Serres, nápadných poměrně nízkou klíěivostí pylu. Jejich diploidní po?et chromosom? byl potyrzen.     

Chromosome numbers and morphology in Cathaya

The authors have for the time observed that somatic cell of Cathaya argyrophylla contains 24 chromosomes (2n=24) (plate I, 3). One pair of them are subtelocentric chromosomes and the rest are metacentric or submetacentric (Fig. 1). This shows that Cathaya is similar to most of genera in Pinaceae in chromosome numbers, but different from Pseutotsuga (2n-26). It seems that Cathaya is not closely related to Pseudot-suga, although its wood anatomy is very similar to that of Pseudotsuga.     

Chromosome numbers in the genus Mentha L.

One hundred and fifty-seven chromosome numbers of a range of taxa from both hemispheres are reported in the genus Mentha. Plants of both wild and cultivated origin have been sampled, including hybrids, some of which have been synthesized from known parents. Some of the causes of the great taxonomic complexity of the group are discussed and the need for accurate and unambiguous identification of the plant material is stressed. There is a critical review of the chromosome numbers in relation to their taxonomy, with a discussion on probable basic numbers. The most useful areas of future research are indicated.