CHROMOSOME COUNTS,CYTOLOGY, AND REPRODUCTION IN THE CACTACEAE

Chromosome counts and observations of reproduction for 55 taxa of Cactaceae indicate that polyploidy is correlated with self-fertility, adventive embryony, profuse branching, and vegetative reproduction. Six genera (Blossfeldia. Cleistocactus, Frailea, Pelecyphora, Rebutia, and Strombocactus) and 35 species or varieties are reported here for the first time. Preliminary observations of pachytene and diplotene indicate that these stages may be more useful in chromosome recognition than mitotic stages. Secondary association at metaphase I and II is interpreted as a retention of homologue association at interphase I and II (interkinesis). During meiosis of certain species, Feulgen negative bodies are present. The production of an abnormal premeiotic division is suggested as a mechanism for polyploid origin.     

CHROMOSOME NUMBERS IN CHEILANTHES AND POLYPODIUM

Six chromosome observations are reported, two being confirmations and four being new counts. Polypodium plesiosorum (from Mexico) shows 37 pairs at meiotic metaphase and thus conforms to past counts of diploid species in this genus. Cheilanthes wrightii (Arizona) has 2n = 58 and is a diploid member of the x = 29 series of that genus. Cheilanthes tomentosa (Alabama) shows 90 units at metaphase of meiosis and approximately the same number during mitosis in the crozier cells. It has 32 spores and our plant is an apogamous triploid. Both Cheilanthes siliquosa (Washington) and C. californica (California) show 30 pairs at meiotic metaphase. Counts on plants identified as C. carlotta-halliae (California) show 30 bivalents and 30 univalents at diakinesis, suggesting that they actually represent allopolyploid backcrosses of C. carlotta-halliae and one of its parents.     

CHROMOSOME COUNTS OF COMPOSITAE FROM MEXICO AND THE UNITED STATES

Chromosome counts of Compositae are reported from Mexico and the United States. First generic counts are from Egletes (n = 27), Hydropectis (n = 9), and Pippenalia (2n = ca. 60). First counts also are reported for 22 specific and infraspecific taxa in Baccharis, Erigeron, Flaveria, Gnaphalium, Grindelia, Helenium, Heterotheca, Melampodium, Montanoa, Perymenium, Piqueria, Senecio, Stevia, Verbesina, Xanthocephalum, and Zaluzania. Additional counts also are provided for 123 populations of taxa counted previously, of which eight are new numbers. Taxonomic implications of certain counts are discussed.     

CHROMOSOME NUMBERS OF HAWAIIAN FLOWERING PLANTS AND THE SIGNIFICANCE OF CYTOLOGY IN SELECTED TAXA

Chromosome numbers are reported for 128 species of flowering plants indigenous or endemic to Hawaii, including first reports for 13 genera and 82 species. The special significance of reports for Ilex, Tribulus, Keysseria, Pisonia, Boerhavia, Jacquemontia, Claoxylon, Lipochaeta, Railliardia, and Dubautia are discussed. The cytological and morphological variation in Railliardia and Dubautia is considered and their treatment as congeners is advocated. The cytogeogruphic pattern in Dubautia and Railliardia and other factors suggest that the ancestral chromosome number of the Hawaiian tarweeds is n = 14. Their derivation from a western North American progenitor similar to Adenothamnus is considered plausible if not indeed likely.     

CHROMOSOME COUNTS OF COMPOSITAE FROM THE UNITED STATES AND MEXICO

Chromosome counts are reported for 126 taxa representing 122 species and 61 genera of Compositae. First reports include two genera, Stylocline (n = 14) and Chromolepis (n = 19), 17 species, two infraspecific taxa, and one interspecific hybrid. Five additional taxa have chromosome numbers differing from previously published accounts. Carminatia is reinstated to generic status.     

CHROMOSOME NUMBERS IN CHEILANTHES,NOTHOLAENA, LLAVEA AND POLYPODIUM

The chromosome numbers of 10 previously uncounted species in Cheilanthes and 1 species of Notholaena are reported. Several confirmatory counts are also listed. One of the plants, Cheilanthes parryi, should probably be retained in the genus Notholaena. Four plants are sexual diploids, three are diploid apomicts, four are triploid apomicts, and three are tetraploids.     

东亚植物区系中若干双子叶植物的染色体新计数及其系统学和进化意义

本文报道了东亚植物区系中双子叶植物9个种的体细胞染色体新计数,其中6个是属的新计数,并对这些资料与有关的科或属在系统学和进化上的意义作了讨论。     

CYTOLOGICAL STUDIES IN THE GENUS DESMODIUM; SOME CHROMOSOME COUNTS

Chromosome counts for 30 collections representing 21 species examined by the authors are reported. Of these, eight species counts are a first report; the others are confirmation of earlier reports. The genus Desmodium is shown to be dibasic with base chromosome numbers of x = 10 and x = 11.     

CHROMOSOME NUMBERS IN CUPHEA (LYTHRACEAE): NEW COUNTS AND A SUMMARY

The American genus Cuphea with ca. 260 species is extremely diverse with respect to chromosome number. Counts are now available for 78 species and/or varieties, or 29% of the genus. Included in this study are first reports for 15 taxa from Brazil, Cuba, Dominican Republic, Mexico, and Venezuela. Twenty-two different numbers are known for the genus, ranging from n = 6 to n = 54. The most common number in the primary center of species diversity in Brazil is n = 8, which is regarded as the base number of the genus. Two numbers are most common in the secondary center in Mexico, n = 10 and n = 12. Species with n = 14 or higher are considered to be of polyploid origin. Polyploids comprise 46% of the total species counted and appear in 9 of the 11 sections for which chromosome numbers have been reported. Aneuploid species comprise ca. 25% of the genus and are known from 7 of the 11 sections. The two subgenera are not characterized by different chromosome numbers or sequences of numbers. None of the 14 sections are circumscribed by a single chromosome number. Morphological and ecological variability in widespread, weedy species is correlated with differing chromosome numbers in some species whereas in others the chromosome number is stable. Summary of chromosome numbers by taxonomic section is presented. Section Euandra, centered in eastern Brazil, and the largest section of the genus, appears to be chromosomally most diverse. In section Trispermum, characterized by difficult, variable species with intermediate forms, two of the four species studied have polyploid races. Section Heterodon, endemic to Mexico and Central America and comprising most of the annual species of the genus, is best known chromosomally. Chromosome numbers have been counted for 25 of 28 species, and 12 different numbers are reported. The most advanced sections, Melvilla and Diploptychia, with numerous species occurring at higher altitudes, are characterized by high polyploids. Apomictic species occur in sect. Diploptycia. The cytoevolution of Cuphea is complex with frequent polyploid and aneuploid events apparently playing a significant role in speciation in both centers of diversity.     

CHROMOSOME COUNTS OF LATIN AMERICAN COMPOSITAE

Chromosome numbers are reported for 111 species of Compositae from Argentina, Chile, Costa Rica, Guatemala, Mexico, Paraguay, and Peru. These include first reports for 46 taxa, including 3 genera (Kyrsteniopsis K. & R.: N = 10, Eupatoriastrum Greenman: N = 16, and Piptothrix B. L. Robins.: N = ca. 17). The new combination, Decachaeta pyramidalis (B. L. Robins.) Sundberg, Cowan, & Turner, based on Piqueria pyramidalis B. L. Robins. is proposed.     

CHROMOSOME COUNTS AND TAXONOMIC NOTES FOR COMPOSITAE FROM THE UNITED STATES AND MEXICO

Chromosome counts are reported for 167 taxa representing 160 species and 76 genera of Compositae. First reports for 27 species and 2 infraspecific taxa are included. New chromosome numbers are reported for 9 additional taxa. The genus Carminatia DC. is merged with Brickellia Ell. resulting in two new combinations: Brickellia tenuiflora (DC.) Keil & Pinkava and Brickellia recondita (McVaugh) Keil & Pinkava.     

CHROMOSOME COUNTS OF COMPOSITAE FROM LATIN AMERICA

Chromosome counts of Compositae are reported from Mexico, Central America, Ecuador, and Chile. First counts are reported for 20 species in Baccharis, Calea, Erigeron, Eupatorium, Heliopsis, Isocarpha, Liabum, Monactis, Pinaropappus, Senecio, Sigesbeckia, Simsia, Spilanthes, Verbesina, and Viguiera. Additional counts also are provided for 65 populations of taxa counted previously, of which 10 are new numbers. The systematic implications of certain of these counts are discussed.     

蕨类植物细胞学概说

<正> 现代蕨类植物细胞学是1950年Irene Manton教授创始的,在她的创造性著作《蕨类植物的细胞学与进化问题》(Problems of Cytology and Evolution in the Pteridophyta.1950)中,提出了主要是产于欧洲的27属和90种蕨类植物的细胞学证据。这本经典著作是相当大的、相当综合的和相当细致的,它激发了这一研究领域中的高潮。现在这     

THE SPORE PATTERN IN SOME SPECIES OF CHEILANTHES

Of the 32 taxa examined, 13 contained 32 spores in each sporangium and are considered apo-gamous, 14 were sexual species with 64 spores per sporangium, and 5 had 32 spores in some sporangia and 64 in others. When considered as a whole, the spores ranged in size from 29.9 to 74.88μ. Most species had oval or globose spores but several had tetrahedral spores. The spores of all were radially symmetrical. Almost all of the species possessed a crassimarginate type of laesura and all except C. cooperae and C. viscida had a perispore. The ornamentation of the perispore showed the following patterns: napate, granulate, psilate, lobate, foveate, and echinate. The exine pattern was predominantly psilate but foveate, rugulate, napate, and granulate conditions were observed. Seventeen taxa were found to have some degree of spore abortion.