Saxifraga Research Articles

Saxifraga banmaensis and S. dingqingensis, two new species of the Saxifragaceae from China

Saxifraga banmaensis J. T. Pan and S. dingqingensis J. T. Pan, two species of the genus Saxifraga (Saxifragaceae) from China, are described and illustrated. Of these, S. banmaensis J. T. Pan is known only from Banma County, Qinghai Province, and related to S. umbellulata Hook. f. & Thoms. (including varieties), but differs by having sepals cartilaginous-mucronulate at apex, and petals linear, not pandurate-oblong to pandurate, base not unguiculate. S. dingqingensis J. T. Pan occurs in Dingqing County, Xizang, and is similar to S. llonakhensis W. W. Smith, but differs by having sepals 3-veined, veins confluent at apex, petals 8-callose, 4-5-veined, base truncate or subauriculate. Both species are endemic to China, and belong to subsect. Rosulares Gornall.

Plant diversity and conservation status of Nanda Devi National Park and comparison with highland National Parks of the Indian Himalayan Region

This paper addresses the plant diversity and conservation status of Nanda Devi National Park (NDNP) and compares these with the Valley of Flowers National Park (VOFNP) and Great Himalayan National Park (GHNP). In the NDNP, 490 species belonging to 281 genera and 89 families of Angiosperms and Gymnosperms have been recorded. Maximum species were represented in the family Rosaceae, genus Saxifraga, altitude zone (3800 m) and alpine pasture/slopes habitat. Twenty-eight families were monotypic. 73% of species were native, 2% were endemic and 34% species were near endemic. Eight species have been recorded in the Red Data Book of Indian Plants and 37 species categorized as Critically Endangered, Endangered, Vulnerable and Low Risk Near Threatened using IUCN criteria. The comparisons of diversity, nativeness, endemism and rarity of the species of NDNP with VOFNP and GHNP indicated that the species diversity was lowest in the NDNP. However, the richness of native and rare endangered species was higher. The richness of endemic species of NDNP was higher than in the GHNP, but lower than in the VOFNP. Monitoring of plant diversity including populations of rare endangered and endemic species is suggested for the effective management of these National Parks.

Elucidating Deep-Level Phylogenetic Relationships in Saxifragaceae Using Sequences for Six Chloroplastic and Nuclear DNA Regions

To elucidate relationships at deep levels within Saxifragaceae we analyzed phylogenetically a data set of sequences for six DNA regions, four representing the chloroplast genome (rbcL, matK, trnL-trnF, psbA-trnH) and two from the nuclear genome (ITS and expansion segments of the 26S rDNA). A total of 6676 bp was aligned per taxon, 4559 bp and 1878 bp from the chloroplast and nuclear genomes, respectively. Chloroplast and nuclear trees agreed closely, prompting analysis of a combined, six-gene data set. Application of both parsimony and maximum likelihood methods yielded similar topologies. The use of different ITS alignments and the exclusion of hard-to-align ITS regions had little impact on either the final nuclear-based topology, or the shortest trees from the analysis of six genes. The affinities of two monotypic genera (Saxifragella and Saxifragodes) endemic to Tierra del Fuego were elucidated. Saxifragella is an early branching member of the North Temperate genus Saxifraga s. str.; Saxifragodes is sister to Cascadia, a genus endemic to Oregon and Washington. Long-distance dispersal from east Asia or western North America to South America may have played an important role in forming these and other similar disjunctions in the family. A number of well-supported clades are present, including Saxifraga s. str., Micranthes, Saxifragopsis/Astilbe, Chrysosplenium/Peltoboykinia, and the Boykinia and Heuchera groups. The use of additional characters has provided greatly increased resolution and internal support at deep levels. Saxifragaceae comprise two major lineages: Saxifraga s. str. (including Saxifragella) and all other genera of the family (the heucheroids). This major split is accompanied by general biogeographical and morpihological differences. Whereas Saxifraga s. str. is largely arctic to alpine in occurrence, the heucheroid clade is largely temperate in distribution, Saxifraga s. str. has a relatively uniform floral morphology (generally actinomorphic; 5 sepals, 5 petals, 10 stamens, 2 carpels), whereas the heucheroid clade encompasses actinomorphic and zygomorphic forms, as well as variation in the number of sepals, petals, stamens, and carpels. Deep-level relationships within both Saxifraga s. str. and the heucheroid clade are well resolved and supported. A phylogenetic classification of the family is provided.

Phylogenetic Relationships and the Evolution of Ovary Position in Saxifraga section Micranthes

Section Micranthes of the genus Saxifraga (Saxifragaceae) comprises 67 species that are distrib- uted throughout the northern hemisphere. A previous phylogenetic analysis indicates that this section is a lineage distinct from the remainder of Saxifraga. Recent taxonomic treatments have divided section Micranthes into four subsections: Cuneifoliatae, Micranthes, Rotundifoliatae, and Stellares. To investigate the phylogenetic relationships among species in section Micranthes and to test the monophyly of each of the four subsections, we sequenced the chloroplast gene matK for 26 species of section Micranthes. The results of our parsimony analyses suggest that subsections Micranthes and Stellares are each monophyletic. The single taxon of subsec- tion Cuneifoliatae (S. calycina) for which material could be obtained appears within a clade representing sub- section Rotundifoliatae; hence Cuneifoliatae may not be distinct from Rotundifoliatae. Within section Micranthes there exists a high diversity of ovary positions, ranging from what has been described as fully superior to greater than one-half inferior. Examination of this character in light of our matK strict consensus tree indicates that the major trend in gynoecial evolution in section Micranthes has been from an ancestor with what has been termed a superior ovary towards greater inferiority. However, gynoecial evolution in subsection Mi- cranthes is complex, with several apparent reversals towards greater superiority. The genus Saxifraga, as traditionally defined, con- sists of approximately 440 species and is the largest genus in Saxifragaceae s. s. (Webb and Gomall 1989). Saxifraga is distributed throughout the north temperate and Arctic regions, with centers of di- versity in the mountains of Europe, eastern Asia, and western North America. The genus is extreme- ly diverse in morphology, ecology, habit, and cy- tology, which has led to difficulty in defining its limits. For example, Haworth (1812) divided Saxi- fraga into 16 segregate genera (see also Small and Rydberg 1905; Love 1983). However, many inves- tigators prefer a broad interpretation of Saxifraga (e.g., Engler 1872; Engler and Irmscher 1916; Gor- nall 1987; Webb and Gornall 1989). Recent phylo- genetic analyses of cpDNA restriction sites (Soltis et al. 1993), rbcL and matK sequences (Johnson and Soltis 1994, 1995; Soltis et al. 1996), and ITS se- quences (Johnson and Soltis 1998) indicate clearly that Saxifraga is polyphyletic, with species forming two distinct clades-Saxifraga s. s. and Micranthes. The former comprises most of the 15 sections tra- ditionally placed in Saxifraga, whereas the Micran- thes clade includes Saxifraga section Micranthes (67 species). The closest relatives of the Micranthes clade appear to be Saxifraga section Merkianae (two spe- cies), and the monotypic Cascadia (= S. nuttallii). Based primarily on features of the seed coat (Kaplin 1981), Webb and Gornall (1989) recognized four subsections within section Micranthes: Micran-

Breeding system, germination, and phenotypic differences among populations of Saxifraga aizoides (Saxifragaceae) at the periphery of its alpine distribution

We investigated breeding system, germination capacity, and phenotypic variation within and among several populations of the arctic‐alpineSaxifraga aizoidesfrom the periphery of its alpine distribution area in Switzerland. Flowers ofS. aizoidesproved to be self‐compatible, but crossing yielded much higher seed set than selfing. Agamospermy did not occur. This result fits well into a general lay‐out of the common breeding system in the genusSaxifraga.Germination of the pioneer speciesS. aizoideswas fast and high in most populations and for most stratification and germination conditions. Nevertheless, a small, isolated population of this species exhibited a lower germination rate, possibly caused by enhanced inbreeding. Phenotypic variation, especially in petal colour and leaf shape, indicated considerable genetic variation within and among populations ofS. aizoides.High germination capacity, successful selfing, and the possibility to maintain substantial intrapopulational genetic variation due to high outbreeding may play decisive roles in the maintenance of biogeographically outlying, relic populations ofS. aizoidesin the Swiss Plateau as well as in the colonization of new habitat patches.

MatK and rbcL Gene Sequence Data Indicate that Saxifraga (Saxifragaceae) is Polyphyletic

The large genus Saxifraga, which consists of ≈400 morphologically and cytologically diverse species, has long been considered taxonomically complex. Phylogenetic analysis of over 2500 bp of chloroplast sequence data derived from matK and rbcL was employed to examine relationships among sections of Saxifraga, the segregate genera Zahlbrucknera, Saxifragopsis, and Cascadia, and the relationships of these taxa to other Saxifragaceae sensu stricto. Phylogenetic trees resulting from separate analyses of the matK and rbcL sequences were highly congruent; phylogenetic analysis of a combined matK–rbcL data matrix was therefore also conducted. Our analyses indicate that Saxifraga is polyphyletic, comprising two well-differentiated clades. One clade, Saxifraga sensu stricto, is the sister to the remainder of the family and consists of Saxifraga sections Irregulares, Heterisia, Trachyphyllum, Cymbalaria, Mesogyne, Xanthizoon, Porphyrion, Ciliatae, Cotylea, Ligulatae, Saxifraga, and Gymnopera. With the exception of Gymnopera, the species-rich sections of this clade are monophyletic. Also part of this clade is the problematic Zahlbrucknera paradoxa, which is allied with members of section Saxifraga. A second major clade of Saxifraga species, Micranthes sensu lato, comprises the large section Micranthes, as well as the segregate genus Cascadia, and S. tolmiei of section Merkianae. This clade is allied with the Heuchera, Darmera, and Chrysosplenium-Peltoboykinia groups of genera. The segregate genus Saxifragopsis is only distantly related to species of Saxifraga, and is instead the sister to Astilbe. The monotypic Oresitrophe is confirmed as a member of the Darmera group of genera. These results suggest that the floral features used to define Saxifraga may simply be symplesiomorphic in these well-separated Saxifraga lineages. Furthermore, the enormous cytological diversity encompassed by Saxifraga likely represents two independent instances of extensive aneuploidy and polyploidy in Saxifragaceae.

MatK and rbcL gene sequence data indicate that Saxifraga (Saxifragaceae) is polyphyletic

The large genus Saxifraga, which consists of ≈400 morphologically and cytologically diverse species, has long been considered taxonomically complex. Phylogenetic analysis of over 2500 bp of chloroplast sequence data derived from matK and rbcL was employed to examine relationships among sections of Saxifraga, the segregate genera Zahlbrucknera, Saxifragopsis, and Cascadia, and the relationships of these taxa to other Saxifragaceae sensu stricto. Phylogenetic trees resulting from separate analyses of the matK and rbcL sequences were highly congruent; phylogenetic analysis of a combined matK–rbcL data matrix was therefore also conducted. Our analyses indicate that Saxifraga is polyphyletic, comprising two well‐differentiated clades. One clade, Saxifraga sensu stricto, is the sister to the remainder of the family and consists of Saxifraga sections Irregulares, Heterisia, Trachyphyllum, Cymbalaria, Mesogyne, Xanthizoon, Porphyrion, Ciliatae, Cotylea, Ligulatae, Saxifraga, and Gymnopera. With the exception of Gymnopera, the species‐rich sections of this clade are monophyletic. Also part of this clade is the problematic Zahlbrucknera paradoxa, which is allied with members of section Saxifraga. A second major clade of Saxifraga species, Micranthes sensu lato, comprises the large section Micranthes, as well as the segregate genus Cascadia, and S. tolmiei of section Merkianae. This clade is allied with the Heuchera, Darmera, and Chrysosplenium‐Peltoboykinia groups of genera. The segregate genus Saxifragopsis is only distantly related to species of Saxifraga, and is instead the sister to Astilbe. The monotypic Oresitrophe is confirmed as a member of the Darmera group of genera. These results suggest that the floral features used to define Saxifraga may simply be symplesiomorphic in these well‐separated Saxifraga lineages. Furthermore, the enormous cytological diversity encompassed by Saxifraga likely represents two independent instances of extensive aneuploidy and polyploidy in Saxifragaceae.

Molecular Systematics of Saxifragaceae Sensu Stricto

To circumscribe Saxifragaceae sensu stricto better, as well as to elucidate generic relationships within this group, we sequenced the chloroplast gene rbcL and its 3' flanking region (yielding 1,471 bp) from 19 genera considered to represent core members of Saxifragaceae. In addition, we conducted a restriction site analysis of chloroplast DNA (cpDNA) for 21 core genera using 23 restriction endonucleases. Phylogenetic analyses using both data sets corroborate the results obtained from surveying the distribution of the loss of the intron in the chloroplast gene rp/2 in delimiting a well-defined Saxifragaceae sensu stricto. Within the Saxifragaceae s.s. clade, a number of poorly resolved, basal phylogenetic branches supports the hypothesis that Saxifragaceae s.s. radiated rapidly very early in its evolutionary history. Molecular data also indicate the presence of several strongly supported groups of genera, such as the Boykinia group (Boykinia, Suksdorfia, Bolandra, Sullivantia, Jepsonia, and Telesonix), the Heuchera group (Heuchera, Bensoniella, Conimitella, Eìmera, Lithophragma, Mitella, Tellima, Tiarelia, and Tolmiea) the Leptarrhena/Tanakaea group, and the Darmera group (Darmera, Astilboides, Mukdenia, Bergenia, and Rodgersia). Significantly, molecular data suggest that the very large, taxonomically complex genus Saxifraga may not be monophyletic. DNA data have also helped to resolve the generic relationships of problematic taxa, indicating, for example, that Telesonix and the enigmatic Jepsonia are sister taxa. In addition to its phylogenetic implications, this study provides insight into basic trends in morphological, chemical, and cytological evolution within Saxifragaceae s.s. The molecular-based phylogenies suggest multiple origins and/or losses of several classes of flavonoid compounds, as well as several independent instances of reduction in stamen and petal number, hypanthium-ovary fusion, and aneuploidy. This study also illustrates the ability of rbcL sequence data to resolve generic-level relationships in some taxonomic groups.

Molecular systematics of Saxifragaceae sensu stricto

To circumscribe Saxifragaceae sensu stricto better, as well as to elucidate generic relationships within this group, we sequenced the chloroplast gene rbcL and its 3' flanking region (yielding 1,471 bp) from 19 genera considered to represent core members of Saxifragaceae. In addition, we conducted a restriction site analysis of chloroplast DNA (cpDNA) for 21 core genera using 23 restriction endonucleases. Phylogenetic analyses using both data sets corroborate the results obtained from surveying the distribution of the loss of the intron in the chloroplast gene rp/2 in delimiting a well‐defined Saxifragaceae sensu stricto. Within the Saxifragaceae s.s. clade, a number of poorly resolved, basal phylogenetic branches supports the hypothesis that Saxifragaceae s.s. radiated rapidly very early in its evolutionary history. Molecular data also indicate the presence of several strongly supported groups of genera, such as the Boykinia group (Boykinia, Suksdorfia, Bolandra, Sullivantia, Jepsonia, and Telesonix), the Heuchera group (Heuchera, Bensoniella, Conimitella, Eìmera, Lithophragma, Mitella, Tellima, Tiarelia, and Tolmiea) the Leptarrhena/Tanakaea group, and the Darmera group (Darmera, Astilboides, Mukdenia, Bergenia, and Rodgersia). Significantly, molecular data suggest that the very large, taxonomically complex genus Saxifraga may not be monophyletic. DNA data have also helped to resolve the generic relationships of problematic taxa, indicating, for example, that Telesonix and the enigmatic Jepsonia are sister taxa. In addition to its phylogenetic implications, this study provides insight into basic trends in morphological, chemical, and cytological evolution within Saxifragaceae s.s. The molecular‐based phylogenies suggest multiple origins and/or losses of several classes of flavonoid compounds, as well as several independent instances of reduction in stamen and petal number, hypanthium‐ovary fusion, and aneuploidy. This study also illustrates the ability of rbcL sequence data to resolve generic‐level relationships in some taxonomic groups.

A manual of saxifrages and their cultivation

A manual of saxifrages and their cultivation

Anthocyanin patterns of european Saxifraga species

Anthocyanin content of 31 European species in the genus Saxifraga was compared. Thirteen anthocyanins were isolated of which 12 were wholly identified as the 3-glucosides and 3,5-diglucosides of delphinidin, cyanidin, petunidin, peonidin and malvidin, and as the 3-galactoside and 3-arabinoside of cyanidin. Generally, the anthocyanin patterns confirm modern subsection division, but not always section division.

An outline of a revised classification of Saxifraga L.

A revised classification of Saxifraga is presented in which 15 sections, 19 subsections and 34 series are recognized. A total of 394 names are accounted for, including the following new taxa, combinations and names: series Hirculoideae (Engler & Irmscher) Gornall, stat. nov.; series Lychnitidae (Engler & Irmscher) Gornall, stat. nov.; series Nulanles (Engler & Irmscher) Gornall, stat. nov.; series Cinctae (H. Sm.) Gornall, stat. nov.; series Gemmiparae (Engler & Irmscher) Gornall, stat. nov.; series Spinulosae (C. B. Clarke) Gornall, stat. nov.; subsection Rosulares Gornall, nom. nov.; subsection Serpyllifoliae Gornall, subscct. nov.; subsection Hemisphaericae (Engler & Irmscher) Gornall, stat. nov.; section Merkianae (Engler & Irmscher) Gornall, stat. nov.; subsection Stellares (Engler & Irmscher) Gornall, stat. nov.; series Birostres Gornall, ser. nov.; series Melanocentrae (Engler & Irmscher) Gornall, stat. nov.; series Astasianlhes (Sternberg) Gornall, stat. nov.; subsection Micranthes (Haworth) Gornall, stat. nov.; series Aulaxis (Haworth) Gornall, stat. nov.; series Dermasea (Haworth) Gornall, stat. nov.; series Micranthes (Haworth) Gornall, stat. nov.; scries Aretioideae (Engler & Irmscher) Gornall, stat. nov.; series Juniperifoliae (Engler & Irmscher) Gornall, stat. nov.; series Lilacinae Gornall, ser. nov.; series Marginatae (Engler & Irmscher) Gornall, stat. nov.; series Squarrosae (Engler & Irmscher) Gornall, stat. nov.; series Rigidae (Engler & Irmscher) Gornall, stat. nov.; subsection Engleria (Siindermann) Gornall, stat. nov; series Subsessiliflorae Gornall, ser. nov.; series Oppositiofoliae (Hayek) Gornall, stat. nov.; series Tetrameridium (Engler) Gornall, stat. nov.; subsection Mutatae (Engler & Irmscher) Gornall, stat. nov.; subsection Florulentae (Engler & Irmscher) Gornall, stat. nov.; section Odontophyllae Gornall, sect. nov.; series Biternatae (Engler & Irmscher) Gornall, stat. nov.; subsection Triplinervium (Gaudin) Gornall, stat. nov.; series Arachnoideae (Engler & Irmscher) Gornall, stat. nov.; subsection Tridactylites (Haworth) Gornall, stat. nov.

Cytologie ultrastructurale de l'anthère de Saxifraga. I. Période d'initiation des précurseurs des sporopollénines au niveau des principaux types exiniques

The period of initiation of sporopollenin precursors studied by transmission electron microscopy in the anthers of three species of the genus Saxifraga (S. cymbalaria ssp. huetiana, sempervivum and clusii) reveals two main phases. They are characterized successively by the elaboration of the ectexine (outer layer of the exine composed of sporopollenin) and endexine (inner layer of the same wall). This phenomenon has been observed in the tapetal periplasm and the sporal periplasm; the latter has been chosen as the reference point in establishing the chronology of the ontogenetic stages as well as the terminology of the sporopollenin structures. Proectexine and proendexine are distinctly stratified in the microspore while they become intermingled in the proorbicules. Proendexine could be elaborated according to a fluid mosaic model in relation to the plasmalemma. During this period, the relationships revealed between the plasmalemma–glycocalyx system (glycolemma) and the cytoskeleton (microtubules, microfilaments, and microfibrils) are emphasized. Thus, their functional role in the setting up of sporopollenin precursors is suggested.

Supernumerary Chromosomes in Saxifraga virginiensis (Saxifragaceae)

Acetocarmine squashes of root tips have demonstrated that 2n = 20 and 38 in Saxifraga virginiensis. These contrast with the earlier reported count of 2n = 28 for this species. In several populations supernumerary chromosomes were detected. Both intrapopulational and interpopulational variation in supernumerary chromosome number were detected, with the largest number of supernumerary chromosomes observed being six. Because these supernumerary chromosomes are equal in size to many of the smaller A chromosomes during mitotic metaphase, the presence of supernumerary chromosomes in this species could not be ascertained by analysis of mitotic metaphase preparations alone. During mitotic prophase, however, the supernumerary chromosomes of S. virginiensis are highly heterochromatic, appearing more densely coiled and darkly stained than the A chromosomes. This characteristic facilitated the recognition of supernumerary chromosomes in this species. The similarity in size of A and supernumerary chromosomes during mitotic metaphase and the observation of six supernumerary chromosomes in one population suggest that the count of 2n = 28 reported earlier for S. virginiensis may actually be a misinterpretation of 2n = 20 plus 8 supernumerary chromosomes. Furthermore, these findings and the observation of this same supernumerary chromosome phenomenon in other species of Saxifraga raise the possibility that some of the many disparate chromosome counts attributed to aneuploidy in the large genus Saxifraga may also be the result of misinterpretations of supernumerary chromosomes as A chromosomes.

SUPERNUMERARY CHROMOSOMES IN SAXIFRAGA VIRGINIENSIS (SAXIFRAGACEAE)

Acetocarmine squashes of root tips have demonstrated that 2n = 20 and 38 in Saxifraga virginiensis. These contrast with the earlier reported count of 2n = 28 for this species. In several populations supernumerary chromosomes were detected. Both intrapopulational and interpopulational variation in supernumerary chromosome number were detected, with the largest number of supernumerary chromosomes observed being six. Because these supernumerary chromosomes are equal in size to many of the smaller A chromosomes during mitotic metaphase, the presence of supernumerary chromosomes in this species could not be ascertained by analysis of mitotic metaphase preparations alone. During mitotic prophase, however, the supernumerary chromosomes of S. virginiensis are highly heterochromatic, appearing more densely coiled and darkly stained than the A chromosomes. This characteristic facilitated the recognition of supernumerary chromosomes in this species. The similarity in size of A and supernumerary chromosomes during mitotic metaphase and the observation of six supernumerary chromosomes in one population suggest that the count of 2n = 28 reported earlier for S. virginiensis may actually be a misinterpretation of 2n = 20 plus 8 supernumerary chromosomes. Furthermore, these findings and the observation of this same supernumerary chromosome phenomenon in other species of Saxifraga raise the possibility that some of the many disparate chromosome counts attributed to aneuploidy in the large genus Saxifraga may also be the result of misinterpretations of supernumerary chromosomes as A chromosomes.

New Taxa of Apiaceae, Hydrophyllaceae and Saxifragaceae from Oregon and Idaho

One new taxon from Idaho,Saxifraga bryophora A. Gray var.tobiasiae, and two from Oregon,Cymopterus acaulis (Pursh) Raf. var.gree-Ieyorum andPhacelia lutea (Hook. & Arn.)J. T. Howell var.mackenzieorum are described and compared with their nearest relatives.

Studies on the Transport of Tritiated Indol-3-ylacetic Acid in Stolons of Saxifraga sarmentosa

Studies on the Transport of Tritiated Indol-3-ylacetic Acid in Stolons of Saxifraga sarmentosa

The Constitution of Saxifraga stolonifera Meerb. I.

The authors have studied to elucidate the constituents of the volatile oil Saxifraga stolonifera Meerb.The volatile oil was treated with 2N-sodium carbonate, then with 2N-sodium hydroxide solution, and was separated into the three parts; neutral, sodium carbonatesoluble, and sodium hydroxide soluble part.Each part was investigated by means of column chromatography, gas chromatography, infrared spectrum, mass spectrum, nuclearmagnetic resonance spectrum and chemical method.As a result, forty eight kinds of compound were detected as the constituents of this volatile oil as follows leaf alcohol, α-pinene, camphene, 1, 4-cineole, limonene, linalool, borneol, citronellol, linalyl acetate, geraniol, bornyl acetate, α-terpinyl acetate, geranyl acetate, dodecanal, β-elemen, α-cedrene, calamenene, n-C17H36, n-C18H38, n-C19H40, iso-C20H42, n-C20H42, iso-C21H44, n-C21H44, n-C22H46, iso-C23H48, n-C23H48, n-C24H50, n-C25H52, n-C26H54, n-C27H56, n-C28H58, n-C30H62, n-C31H64, n-C32H66, caprylic acid, capric acid, lauric acid, myristic acid, pentadecanoic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, phenol o-cresol, p-cresol and m-cresol.

Pollen morphology in the genus Saxifraga and its taxonomic significance

Pollen morphology in the genus Saxifraga and its taxonomic significance

STUDIES OF MEIOSIS IN THE GENUS SAXIFRAGA OF THE PACIFIC NORTHWEST

A cytogenetic study of the genus Saxifraga in the Pacific Northwest has been initiated as a contribution toward a better understanding of relationships within the genus. The present paper reports work done on nine species or groups of morphologically similar species and varieties (each group termed a "plexus") which have so far been studied. The nine species or groups of species are S. tolmiei, S. bronchialis, S. integrifolia, S. ferruginea, the S. montanensis plexus, the S. occidentalis plexus, S. odontoloma, S. lyallii and S. mertensiana. Meiosis in pollen mother cells of one species was found to be generally regular, pollen fertility high. In every other species or plexus a variable and sometimes very high degree of meiotic irregularity was present. Pollen fertility was often much reduced. The cause of meiotic disturbances has not yet been discovered. Consideration is given to the ways in which the species may succeed in spite of reduced pollen fertility. Such irregular meiotic divisions would be difficult to use in cytogenetic studies as a standard for comparison with meiosis in artificial hybrids.