CHROMOSOME NUMBERS IN COMPOSITAE. III. SENECIONEAE

Ornduff , Robert (Duke U., Durham, N. C), Peter H. Raven , Donald W. Kyhos , and A. R. Kruckeberg . Chromosome numbers in Compositae. III. Senecioneae. Amer. Jour. Bot. 50(2): 131–139. Illus. 1963.—Chromosome counts are reported for 75 taxa of tribe Senecioneae (Compcsitae) and are listed with a generic summary of previous counts in the tribe. First counts are reported for Bedfordia, Crocidium, Dimeresia, Gamolepis, Lepidospartum, Luina, Peucephyllum, Telradymia, and the first definite count recorded for Euryops. New numbers are added to those previously known in Arnica and Psathyrotes. Intraspecific differences in ploidy-level are reported in 4 North American species of Senecio. Although chromosome numbers are useful as an aid in delimiting some genera of Senecioneae, they are of little use in circumscribing genera peripheral to Senecio, primarily because of the great range of chromosome numbers of that genus. Chromosome numbers support suggestions based on morphological considerations that genera such as Crocidium and Dimeresia do not belong in Senecioneae, whereas chromosome number and morphology of the plants virtually prohibit the removal of such genera as Peucephyllum, Lepidospartum, and Telradymia from Senecioneae, despite the suggestions of several recent authors. It is proposed that the base number for the tribe is 10 and that the tribe originated in the Old World, with subsequent widespread migration and diversification.     

CHROMOSOME NUMBERS IN COMPOSITAE VIII: HELIANTHEAE

One hundred and ninety-three new counts are reported for the tribe Heliantheae of Compositae, mostly based on determinations of meiotic material, including first counts for the genera Adenothamnus, Chrysogonum, Enceliopsis, Guardiola, Isocarpha, Lipochaeta, Otopappus, and Oyedaea, as well as first counts for 66 species. The original counts are discussed in relation to those previously reported for the tribe, by genera and subtribe. Two-thirds of the approximately 150 genera and more than a third of the roughly 1500 species have now been examined. The incomplete knowledge of generic relationships in the tribe often make the interpretation of these chromosome numbers difficult. Three observations are documented and discussed: (1) genera with low chromosome numbers are few; (2) genera with aneuploid series are abundant; and (3) the original basic chromosome number in the tribe is probably in the range of x = 8 to x = 12.     

THE PROBLEM OF PLOIDY IN ECHEVERIA (CRASSULACEAE) I. DIPLOIDY IN E. CILIATA

The largely Mexican genus Echeveria is characterized by an extensive series of dysploid chromosome numbers, with every gametic number from 12 to 34 known in at least one species. Within this nearly three-fold range of numbers, the boundary between diploidy and tetraploidy is not immediately apparent. However, species of Echeveria can be hybridized in an extraordinary number of combinations, both among themselves and with related genera, and study of the morphology of the hybrids and the pairing of their chromosomes provides information that helps to identify the ploidy of the parents. This paper reports observations from study of 80 hybrids between E. ciliata (n = 25) and 73 other species and/or cytotypes. Hybrids between E. ciliata and definite diploids are all nicely intermediate morphologically, whatever the chromosome numbers. In these same hybrids, most chromosomes become involved in pairing at meiosis, and the number of paired elements (bivalents and multivalents) approaches or equals, but never exceeds, the number of chromosomes received from the lower-numbered parent. In most cells, relatively few univalents are present, sometimes none. These observations are considered to indicate that all paired elements include at least one chromosome from each parent and therefore that pairing occurs between chromosomes of different parents only (allosyndesis). Since none of the 25 gametic chromosomes of E. ciliata is able to pair with any other, although they do pair very extensively with chromosomes from many other species having a wide range of numbers, E. ciliata is considered to be diploid in spite of its relatively high chromosome number. On the other hand, hybrids of E. ciliata with definite polyploids resemble the latter much more closely in their morphology, and at meiosis most or all pairing occurs by autosyndesis between chromosomes received from the polyploid parent, while the chromosomes from E. ciliata generally remain unpaired. In these respects most, but not all, species of Echeveria having as many as 34 gametic chromosomes have the same properties as E. ciliata and also are considered to be diploid. The ancestral chromosome number in the genus is not clear, but it is probably near the upper end of the series of dysploid numbers.     

CHROMOSOME COUNTS IN CHEILANTHES AND ASPIDOTIS WITH A CONSPECTUS OF THE CYTOLOGY OF THE SINOPTERIDACEAE

Confirmatory, corrective and new chromosome counts are listed for species in the genus Cheilanthes, and a new chromosome count is given for a member of the genus Aspidotis. An analysis of five collections of C. castanea revealed no significant morphological differences despite the different chromosome numbers. The ploidy level of all known species in genera of the Sinopteridaceae is summarized, revealing directions in which future research might proceed to complete our cytological knowledge of this family.     

CHROMOSOME NUMBERS IN COMPOSITAE. VI. SENECIONEAE. II

Chromosome counts are reported for 76 taxa and 2 natural hybrids of tribe Senecioneae (Compositae). First counts are reported for several species of Senecioneae as well as for the genera Cadiscus and Whitneya. New chromosome numbers are added to those previously known in Arnica, Cacalia, and Senecio. Additional counts from Arnica support our previous suggestion that x = 19 for this genus. It is assumed that observed meiotic irregularities are associated with apomixis in this genus. Basic chromosome numbers for various New World sections of Senecio are proposed, and certain problems of sectional relationships in this genus are discussed. Chromosome numbers and plant morphology of Cadiscus, Hulsea, and Whitneya indicate that these genera should be removed from Helenieae to Senecioneae. The possible affinity of the anomalous genus Adenocaulon with Mutisieae is discussed. Data presented in the paper further support our earlier proposal that the basic chromosome number for Senecioneae is x = 10.     

CHROMOSOME NUMBERS IN THE COMPOSITAE. X. NORTH AMERICAN SPECIES

Chromosome counts from 132 plant populations representing 124 taxa (in 67 genera) are reported. These include previously unreported counts for over 70 species and 5 new generic counts (Hofmeisteria, x = 19; Oxypappus, x = 10; Pterocaulon, x = 10; Stenocarpha, x = 8; and Urbinella, x = 8). Two new base numbers are reported for specieis of Perityle (P. californica, x = 13 and P. palmeri, x = 17), and previously unreported n numbers have been found for species of the genera Bidens (n = 17) and Hymenostephium (n = 21). Several gametic cells with differing meiotic configurations were found in the same head of Stevia viscida (n = 11 pairs; 11 pairs and 11 univalents; 33 univalents). When appropriate, the chromosomal information has been related to systematic problems, especially for genera of the subtribes Flaverinae, Coreopsidinae, Galinsoginae and Peritylinae.     

CHROMOSOME NUMBERS IN COMPOSITAE V. ASTEREAE II.

Reports of 100 new chromosome counts are made for the tribe Astereae of Compositae, mostly based on determinations of meiotic material, including first counts for 9 genera and 53 species. Counts are now available for 58 of the approximately 100–120 genera and 431 of the approximately 2000 species in the tribe. Comparisons are made between chromosome number and habit and also between chromosome number and geographical distribution. Species and genera with a basic number of x = 9 are the most abundant. Within different phyletic lines x = 9 is also the most abundant number. On the other hand, many species with x = 4 and 5, belonging to a number of small, largely annual genera, are concentrated in southwestern North America. The low chromosome number in these plants is probably correlated with the dry habitat they occupy, and is most likely a specialized condition.     

CHROMOSOME NUMBERS AND PHYLOGENY IN MELAMPODIUM (COMPOSITAE)

The haplord chromosome numbers of n = 9, 10, 11, 12, 18, 20, 23, 25 ± 1, 27, 30, and 33 have been reported by various authors from 26 of the 37 recognized species of Melampodium. A chromosomal survey of 375 plants from 275 different populations suggests that the recorded numbers are stable within the genus and that infraspecific euploidy and aneuploidy are uncommon. These chromosome numbers can be arranged numerically, with morphological and limited cytogenetic substantiation, into four euploid series of x2 = 9, 10, 11, and 12. Of these four groups of species, the x = 10 series is the largest and morphologically most diverse. This consideration, along with additional evidence from the morphology of sterile disc ovaries, suggests that x = 10 is the ancestral chromosomal base in Melampodium. A comparison of morphological and cytological data from the closely related genera, Acanthospermum and Lecocarpus, indicates that the latter are probably on a common base of x = 11. Present day distributional patterns of all three genera support the hypothesis that x = 10 is the ancestral base for the entire complex.     

CHROMOSOME NUMBERS IN THE PHASEOLEAE (FABACEAE:FABOIDEAE) AND THEIR RELATION TO TAXONOMY

Chromosome numbers are reported for 33 species of the tribe Phaseoleae. Six reports are first counts for their species; one report (Ophrestia hedysaroides) is a first count for the genus. This increases the number of genera counted to 53 out of a total 84 for the tribe. A survey of base numbers shows a general pattern of numbers 10 or 11, the same base numbers as in the neighboring tribes Dalbergieae sensu lato, Galegeae sensu lato, and Abreae. The chromosomes are generally small and polyploidy is uncommon. Deviations from base numbers 10 or 11 are mostly found in those genera with morphological pecularities and puzzling taxonomic placements: Erythrina (21), Clitoria (8, 11, 12), Butea (9), Calopogonium (18), Teramnus (14), and Strongylodon (14). Two genera have base numbers which suggest derivation by polyploidy: Glycine (20) and Cologania (22).     

CHROMOSOME NUMBERS IN THE HYPOCREALES 1. NUCLEAR DIVISION IN THE ASCUS OF NECTRIA PEZIZA

El -Ani , Arif S. (Columbia U., New York, N. Y.) Chromosome numbers in the Hypocreales. 1. Nuclear division in the ascus of Nectria peziza. Amer. Jour. Bot. 46(6): 412–417. Illus. 1959.—The 4 nuclear divisions in the ascus of Nectria peziza were studied with the aid of acetoorcein and aceto-carmine techniques. The ascus was found to arise by crozier formation. Synapsis takes place while the chromosomes are still contracted and elongation of chromosomes continues throughout the pachytene phase. The haploid complement was found to consist of 5 chromosomes, the second of which is the nucleolus-organizing chromosome. This chromosome number which had never been reported in the Hypocreales was also found in several other species of this group of fungi. Chromosome numbers in the Hypocreales are discussed with regard to the species concept in the imperfect genus Fusarium.     

Cytotypes within the family Umbelliferae with special reference to the genera Seseli L. and Oenanthe L. (subtribe Seselinae)

Cytotypes within the genera Seseli L. and Oenanthe L. show variation in chromosome number in pollen mother cells. A correlation of low chiasma frequency with meiotic irregularities and pollen sterility was noted. In addition to the meiotic irregularities in the two genera occurrence of polyspory and triple pollen formation during meiosis have been observed in Seseli diffusum (Roxb.) Sant. Wagh. The presence of different chromosome numbers in different populations of the same species and karyological investigation in 4 species of Oenanthe L. suggests that structural changes of chromosomes associated with numerical differences have possibly played a role in their evolution. Diminution in chromosome size and complete absence of metacentric chromosomes in Oenanthe lachenalli Gmel. suggest that probably this species is more evolved than 3 species of Oenanthe (i.e., O. benghalensis Benth., O. pimpinelloides L. and O. thomsoni Clarke). The interrelationships of the two genera are discussed.     

THE PROBLEM OF PLOIDY IN ECHEVERIA (CRASSULACEAE) II. TETRAPLOIDY IN E. SECUNDA

Every chromosome number from n = 12 to n =34 and also many higher numbers are known in one or more of the 130+ species of Echeveria, and the numerical boundary between diploids and tetraploids is not immediately apparent. Echeveria also is extraordinary for the number and diversity of hybrids that it can produce in cultivation, both within the genus and with species of several related genera. In 42 collections studied, the morphologically and cytologically variable E. secunda of central Mexico has n = 30-32, often with one or more B-chromosomes, and some quadrivalents are formed at meiosis in nearly every cell. Twenty-four hybrids of E. secunda, with 22 species or cytotypes considered diploids, resemble the former much more closely in appearance, and at meiosis 15-16 paired elements (bivalents and multivalents) are formed, never more, regardless of the number of chromosomes, 12 to 34, that were received from the other parent. It is concluded that the 15-16 paired elements in these hybrids are formed by the 30-32 chromosomes received from E. secunda, and that most chromosomes from the other parents occur as univalents, although usually a few associate with pairs from E. secunda to produce multivalents. Hybrids of E. secunda with 11 definitely tetraploid species having n = 34 to n = 68 are nicely intermediate in morphology between their parents, form mostly or entirely bivalents at meiosis, and most, probably all, including five intergeneric hybrids, are fertile. These observations are all consistent with the conclusion that E. secunda is an autotetraploid, even though no plants of the species having n = 15 or 16 have been found, and even though some other species of Echeveria having as many as 34 gametic chromosomes appear to be effectively diploid. Observations on pollen stainability and on second-generation hybrids are all compatible with this conclusion. The high chromosome numbers in many Mexican Crassulaceae that are now effectively diploid may have originated as polyploids that have become diploidized by mutation, loss, or suppression of duplicated chromosomes, segments, and genes. Hybrids of E. secunda, with three other species that appear to be tetraploids, have less regular meiosis, apparently because all of the chromosomes from the other parents do not regularly form pairs in the hybrids. These three species may represent intermediate stages in the processes of diploidization.     

CHROMOSOMAL RELATIONSHIPS AND TAXONOMIC CONSIDERATIONS IN THE GENUS CASSIA

Irwin , H. S. and B. L. Turner . (U. Texas, Austin.) Chromosomal relationships and taxonomic considerations in the genus Cassia. Amer. Jour. Bot. 47(4): 309-318. 1960.—All chromosome numbers known for the genus Cassia are arranged in a table which follows the infrageneric organization of Bentham (1871). Included are new counts for 88 taxa, of which 68 are first reports. Evidence is represented which suggests that the base number for the genus is 7, the other numbers having been derived by aneuploid loss from various euploid levels. The basic number 8, of general occurrence in the Subsection Leiocalyx, Section Chameacrista, is presumed to have been derived from the ancestral generic base by aneuploid gain of 1 chromosome. The results of the present study do not support elevation of the section Chamaecrista to generic rank. In general, the basic soundness of Bentham's revision is upheld.     

BIOSYSTEMATIC INVESTIGATIONS IN THE GENUS AGROPYRON. I. CYTOLOGICAL STUDIES OF SPECIES KARYOTYPES

Schulz -Schaeffer , Jurgen (Montana State Coll., Bozeman), and Peter Jurasits . Biosystematic investigations in the genus Agropyron. I. Cytological studies of species karyotypes. Amer. Jour. Bot. 49(9): 940–953. Illus. 1962.—Twenty-five species of the genus Agropyron are analyzed cytologically in this presentation. Accession numbers, names of collectors, locations where seed was collected, and observed chromosome numbers are listed. Chromosome numbers of A. panormitanum (2n = 28), A. lolioides (2n = 58), A. brachyphyllum (2n = 42), A. ciliatiflorum (2n = 28), A. kosanini (2n = 56), A. pseudorepens (2n = 28), A. squamosum (2n = 42), and A. subulatum (2n = 56) are reported. No previous counts in these species are known to the authors. Chromosome counts of A. caespitosum (2n = 42) and A. elongatiforme (2n = 58), deviate from previous reports. Idiograms of all species and photomicrographs of mitotic metaphase root tip cells of 14 species are presented. The distribution of 11 satellite-chromosome types in 25 Agropyron species is shown in Table 2. The proportions of these 11 satellite-chromosome types are recorded in Table 3. The significance of these satellite chromosomes as indicator chromosomes for genome relationships is discussed together with the pertinent literature.     

PTEROCARYOID FRUITS (JUGLANDACEAE) IN THE PALEOGENE OF NORTH AMERICA AND THEIR EVOLUTIONARY AND BIOGEOGRAPHIC SIGNIFICANCE

The Juglandaceae (walnut family) has an excellent fossil record of various organs extending back to the earliest Tertiary. Several genera which today are restricted to isolated geographic regions were widespread in the Northern Hemisphere during the Tertiary. This paper focuses upon the fossil record of the Pterocarya alliance of the subfamily Juglandoideae, tribe Juglandeae. The Pterocarya alliance includes only two modern genera, Pterocarya (five species) and Cyclocarya (one species), both restricted to Eurasia. Paleogene sediments of the Rocky Mountain Region have yielded three genera and four species referable to the Pterocarya alliance: Cyclocarya (two species), Pterocarya, and a new genus, Polyptera. Although three of the four Paleogene species described here are attributed to present day genera, each represents an extinct form, which cannot be accommodated by any single living species. These fossils, reviewed with other published reports, indicate that the Pterocarya alliance, like the Engelhardia alliance of the same family, was more diverse and much more widespread geographically in the Tertiary than it is today.     

CHROMOSOME NUMBERS IN COMPOSITAE. IX. HAPLOPAPPUS AND OTHER ASTEREAE

Reports of 209 original chromosome counts are made for the tribe Astereae of Compositae, including first counts for two genera and 46 species or subspecies. With over 80 % of the species counted, chromosome numbers are now available for all North American sections of Haplopappus. Two major groupings are apparent: one, with basic numbers of x = 4, 5, or 6, is basically herbaceous; the other, with x = 9, consists of shrubs or subshrubs. Aneuploidy is known only in the “herbaceous” group of Haplopappus, and polyploidy is more extensive there than in the woodier group of sections.     

Chromosome numbers of Thai Rubiaceae

Chromosome numbers for 14 taxa of indigenous Thai Rubiaceae are presented. They include first counts for 3 genera: Aphaenandra (A. uniflora), Prismatomeris (P. tetrandra subsp. malayana) and Tarennoidea (T. wallichii) ; all show diploidy on x=11. The remaining counts are first counts for species: Argostemma diversifolium, A. neurocalyx and A. pictum, Coptosapelta flavenscens, Gardenia saxtilis, Ixora sp., Morinda sp., Mussaenda sanderiana, Oxyceros horridus, Rothmannia wittii (first count for an Asiatic species of the genus) (all diploid on x=11), and Canthium sp. (tetraploid on x=11). The poor state of karyological knowledge of indigenous Thai Rubiaceae is discussed, and a table including all relevant known chromosome counts is presented. Chromosome data are only known for 38 genera (ca. 41% of all Rubiaceae genera occurring in Thailand); chromosome numbers are often only available for one or few taxa of each genus [in sum, for only about 50 (or for roughly 10% of all) taxa]. Of only 14 genera (ca. 15%), chromosomes were counted from Thai material (for the others, counts originate from elsewhere, i.e. refer to more widely distributed taxa also extending into Thailand).     

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 THE LEGUMINOSAE. III. SPECIES OF THE SOUTHWESTERN UNITED STATES AND MEXICO

Turner, B. L., and Olin S. Fearing. (U. Texas, Austin.) Chromosome numbers in the Leguminosae. III. Species of the Southwestern United States and Mexico. Amer. Jour. Bot. 47(7) : 603–608. Illus. 1960.—Chromosome counts for 43 species of the Leguminosae from the southwestern United States and Mexico have been reported. These include first reports for 42 taxa of which 16 are for the subfamily Mimosoideae. Olneya tesota (2n = 18) is the only new generic count listed. Chromosome reports of particular significance include a single polyploid count for a North American species of Acacia, as well as diploid and tetraploid counts for closely related taxa in this genus. Four species of the genus Schrankia were found to be diploid with In = 26, indicating a base of x = 13 instead of the x = 8 reported by some previous workers. Leucaena pulverulenta was found to have a diploid count of 2n = 56 indicating a base of x = 14.     

CHROMOSOME NUMBERS IN THE COMPOSITAE. XII. AUSTRALIAN SPECIES

Chromosome counts are reported for plants from 171 populations of Australian Compositae; most of these are first reports for the approximately 104 taxa distributed among 37 genera. New generic counts with base numbers indicated include: Astereae —Bellida (x = 9), Minuria (x = 9); Inuleae —Angianthus (x = 12, 13), Calocephalus (x = 7), Cephalipterum (x = 12, 14), Craspedia (x = 11), Gnaphalodes (x = 10), Gnephosis (x = 4, 12), Myriocephalus (x = 6), Isoetopsis (x = 17); Calenduleae —Tripteris (x = 8); and Artcoideae —Arctotheca (x = 9). Most of the counts were from the tribes Astereae (47) and Inuleae (95). The phyletic import of these data is discussed selectively and comparisons are made with the chromosomal variation found in the Australian desert Compositae with that found in the North American desert Compositae.