Petal Shape Research Articles

New and Noteworthy Species of Hechtia (Bromeliaceae) from Guerrero, Mexico

Two new species are described in the genus Hechtia: H. carlsoniae and H. pumila. Hechtia melanocarpa, previously thought to be known only from its type, is represented by several collections. In contrast to the type specimen which is of horticultural origin, collections from the type locality have consistently larger inflorescences with elongate lateral branches. Moreover, sta- minate and pistillate individuals differ significantly in inflorescence form and petal shape. Hechtia Klotzsch is a genus of about 50 species

A Systematic Re-Evaluation of Phacelia mohavensis var. exilis (Hydrophyllaceae)

Phacelia mohavensis var. mohavensis and P. mohavensis var. exilis are distinct entities that differ in their stamen length; petal, pollen, and filament color; petal shape and orientation; petal venation patterns; and leaf morphology. As consequence of these differences, P. mohavensis var. exilis is considered to be distinct species: P. exilis. Both species have haploid chromosome number of n = 9. Phacelia mohavensis A. Gray is montane an- nual of southern California, ranging from the Greenhorn Mts. of southern Tulare Co. to dis- junct populations in Ventura, Los Angeles, and San Bernardino cos. Asa Gray first described the species and Phacelia mohavensis var. exilis in 1878. Eventually he treated the variety as a slender erect form of the species (Gray 1880), treat- ment subsequently adopted by Howell (1945), Constance (1951), and Munz (1959). My field, greenhouse, and herbarium studies of popula- tions from throughout the range of the two taxa were conducted after initial field observations indicated consistent and substantial morpho- logical differences between the taxa originally described by Asa Gray. This paper re-examines and clarifies their status in light of those dif- ferences.

Morphological and chemical variations in natural populations of Pituranthos triradiatus in the Negev Desert

Morphochemical variations among six populations of Pituranthos triradiatus have been studied in the Negev Desert, in areas located within an air distance of 80 km, with an aridity gradient from 150 to 50 mm of average annual rainfall. Based on morphological florisitic characters, as well as on the content of furanocoumarins in the shoots of the shrub, five different populations have been observed. Some of the morphological characters which are commonly used for classification in the species level were found useful for the subspecies level, e.g. number of rays per umbell or per umbellet. Others, such as the shape of petals or stylopodium, or petals color, were not efficient. In addition to the commonly used characters, average fruit weight was found useful. Seven different furanocoumarins were found in the examined populations of P. triradiatus. Four of them (isoimperatorin, imperatorin, bergapten and isopimpinellin) were in each of the populations studied. Three other furanocoumarins were found to be specific: cnidilin for the Revivim population; pimpinellin for Zin and isobergapten for the Marzeva and Neqarot populations. In addition to these specific furanocoumarins, the amount of bergapten in the shoots seems to be specific for each population and is suggested to be used as a chemical marker for further screening of chemotype differentiation in R. triradiatus. It is suggested that the differences in the floristic characters, as well as in the content of furanocoumarins are of genetic nature and not an artifact. To better establish this view and to evaluate the efficiency of furanocoumarins content as a chemotaxanomic marker, further work is needed. It is also suggested that levels of isolation among the investigated population account for the differences encountered. No association could be found between different levels of aridity and different levels of furanocoumarin content.

Pelargronium divisifolium (Geraniaceae): a new species from the south-western Cape Province

Pelargonium divisifolium Vorster, a new species from the south-western Cape Province, is described. Morphologically it resembles P. sericifolium J.J.A. v.d. Walt on account of its habit, closely spaced pinnately divided leaves, subulate stipules, architecture of the inflorescence, and shape of the petals. It is however distinguished by its much narrower foliar segments ( ca . 1 mm against up to 3 mm wide), macroscopically glabrous instead of densely sericeous leaves, stipules free instead of adnate to the petiole for at least ⅔ of their length, the pedicel being well-developed and more or less equal to the hypanthium instead of inconspicuously short, and the petals being pink or white instead of intense pinkish-purple. This species was previously incorrectly known as P. artemisiifolium DC.

Fine structure of the images of atoms in 011‐gold crystals in various Bragg reflecting conditions

SUMMARYFine structures with petal and horseshoe shape contrast have been observed in the high resolution electron microscope images of atoms in a 011 gold crystal in deviated Bragg reflecting conditions. The images with such fine structures have been recorded by using only the beams of 000, four 111 and two 200 reflections with axial illumination. The contrast of the images has been discussed by the many beam dynamical theory of electron diffraction and the image formation theory considering the spatial and temporal coherence of the electron waves. It has been noted that the temporal coherence has much more effect on the change of image contrast than the spatial coherence. The imaging conditions have been analysed in terms of Fourier images and the aberration free focus conditions.

Fe-C-Cr-Nb合金の凝固組織

The freezing processes and solidification structures of Fe-5%Cr and Fe-15%Cr alloys with 0.5 to 4.7%C and 0 to 7.5%Nb were investigated metallographically. The distribution of alloying elements were also studied by use of E.P.M.A. to clarify the behavior of elements during solidification. The constitutional diagrams for liquidus surfaces of Fe-5%Cr-base alloys and Fe-15%Cr-base alloys were established. In the 5%Cr system primary δ, γ, NbC and M3C phases and eutectic reactions of Liquid→(γ+NbC), Liquid→(γ+M3C) and Liquid→(γ+NbC+M3C) appeared. Primary δ, γ, NbC and M7C3 phases and eutectic reactions of Liquid→(γ+NbC), Liquid→(γ+M7C3) and Liquid→(γ+NbC+M7C3) occurred in the 15%Cr system. Primary niobium carbides grew dendritically and eutectic niobium carbides crystallized in the shape of petal. The amount of NbC increased and that of M3C and M7C3 decreased with increasing niobium content of alloy. During solidification niobium was preferentially partitioned to primary and eutectic NbC, and chromium to M7C3 crystals. The partition ratios of niobium and chromium to primary γ were 0.02 to 0.01 and 0.93 to 0.72, respectively. They decreased with the increase in the carbon content of alloy. The addition of 0.3%Ti to the melt nodularized both primary and eutectic niobium carbides, because many tiny titanium carbide particles precipitated at higher temperatures nucleated the niobium carbides.

Morphological and agronomic description of selectedCuphea germplasm

Forty Cupheaspecies, recently collected in mid- and southern Mexico, are described in terms of their main morphological and agronomic characteristics. In some species, dormancy, slow germination, sticky hairs, and perennial character, as well as poor flowering and low seed yield limit their agronomic potential. However, some species of the section Heterodon show good crop potential. Among these, C. wrightii, C. glossostoma,and C. laminuligeraseem to be the best lauric acid-synthesizing species. Of the capric acid species, C. paucipetala, C. lanceolata,and C. procumbenshave the best growing potential in humid climates, whereas C. leptopodaand C. inflataare well adapted to arid growing conditions. All Cupheaspecies show seed shattering caused by flower zygomorphy. This zygomorphy not only causes different petal shape and a bilateral symmetry of the calyx tube, but also dispersal of the seeds. It represents the main taxonomic trait for characterizing the genus. Flowering and seed setting continue over a period of several weeks due to indeterminate growth. Multiple harvests with vacuum picking systems that do not damage the plants maximize recovered yields.

Development of Flower form in an Allotetraploid Clarkia and Its Parental Diploid Species

The allotetraploid Clarkia delicata possesses a floral phenotype and breeding system intermediate to its diploid progenitors. Three patterns were observed in a comparative study of anther, sepal, and petal development using allometry and scanning electron micrographs. In Pattern 1 (e.g., anther), all three species are similar at inception and in subsequent development. Anthers of the allotetraploid mature at a size intermediate to both diploids. In Pattern 2 (e.g., sepal and petal limb), diploids exhibit divergent developmental patterns, and the allotetraploid develops similarly to one diploid. In Pattern 3 (e.g., petal size and shape), diploids exhibit divergent developmental patterns, and the allotetraploid is variously intermediate to both. In petal size (length vs. width), the diploid developmental pathways are parallel, and the allotetraploid is intermediate at all points of development. In petal shape (limb length above widest point/length below widest point vs. petal width), diploid developmental pathways intersect, and the allotetraploid is similar to one diploid at inception and the other in subsequent development.

DEVELOPMENT OF FLOWER FORM IN AN ALLOTETRAPLOID CLARKIA AND ITS PARENTAL DIPLOID SPECIES

The allotetraploid Clarkia delicata possesses a floral phenotype and breeding system intermediate to its diploid progenitors. Three patterns were observed in a comparative study of anther, sepal, and petal development using allometry and scanning electron micrographs. In Pattern 1 (e.g., anther), all three species are similar at inception and in subsequent development. Anthers of the allotetraploid mature at a size intermediate to both diploids. In Pattern 2 (e.g., sepal and petal limb), diploids exhibit divergent developmental patterns, and the allotetraploid develops similarly to one diploid. In Pattern 3 (e.g., petal size and shape), diploids exhibit divergent developmental patterns, and the allotetraploid is variously intermediate to both. In petal size (length vs. width), the diploid developmental pathways are parallel, and the allotetraploid is intermediate at all points of development. In petal shape (limb length above widest point/length below widest point vs. petal width), diploid developmental pathways intersect, and the allotetraploid is similar to one diploid at inception and the other in subsequent development.

Three-dimensional shape of a body of minimum drag in a hypersonic gas stream

The three-dimensional aerodynamic shape of a slender body of minimum drag is determined. The solution to the corresponding variational problem is considered in a special class of surfaces, among which there are surfaces of revolution. An approximate analytic investigation is made, and the results are given of a numerical calculation by the method of local variations. It is shown that the profile of the transverse section of the optimal body has a petal shape which becomes a circle in the midsection.

GENETIC CONFIRMATION OF THE ORIGIN OF CLARKIA LINGULATA.

Rapid speciation not only confers reproductive isolation in a few generations, but also has the consequence that the alleles of the derivative species are, at its outset, a limited sample of those of its progenitor. Therefore, when evidence from morphology, cytogenetical analysis of chromosome structure, geographical distributions and ecology combine to suggest that one species originated recently from another in a rapid series of events, both species are expected to possess in common a high proportion of their alleles detected by electrophoretic analysis of enzyme variation. I have used gel electrophoresis to examine the amount of genetic differentiation in two pairs of annual plant species that have been considered to have a recent parentoffspring relationship. In both cases, the parental species is widespread and outcrossing, and the derived species highly self-pollinating and found in only a single population. In a derived species of Stephanomeria, presently called Malheurensis, all the alleles but possibly one are also present in its progenitor (Gottlieb, 1973a). But numerous alleles in Clarkia franciscana are not present in its presumed progenitor (Gottlieb, 1973 b). Consequently, the electrophoretic evidence is concordant with the hypothesis of recent origin in the first case but not in the second. Various suggestions can be offered to explain the lack of concordance in C. franciscana but, because they deal with unobserved past events, they are not subject to disproof (Gottlieb, 1973b). The result is that the proposed mode of origin of C. franciscana (Lewis and Raven, 1958) is less certain than that for Malheurensis. Therefore, it became worthwhile to examine genetic differentiation between parent and derivative in another presumed case of recent rapid speciation. For this purpose, I selected an example in which both the derivative and parental species, although capable of self-fertilization, generally outcross: Clarkia lingulata and C. biloba. Clarkia lingulata is known from two sites in the Merced River Canyon, California, at the southern geographical periphery of the distribution of C. biloba. In external morphology, the two species differ only in the shape of the flower petal, but chromosomally they differ by a translocation, several paracentric inversions, and an extra chromosome in C. lingulata which is homologous to parts of two chromosomes of C. biloba (Lewis and Roberts, 1956; Lewis, 1962). Experimental study of the two species under uniform growth conditions failed to demonstrate any conditions of growth in which C. lingulata was better adapted than C. biloba (Lewis, 1969, 1973).

Observations on the morphology, anatomy, classification, and reproductive cycle of Saxifraga ferruginea

A survey of morphology and anatomy has been made in the wide-ranging species, Saxifraga ferruginea Graham (Saxifragaceae), of western North America. Anatomical features are reported in detail and are consistent within the six populations studied.The species has been subdivided in many different ways by many taxonomists on the basis of morphological variability. The characteristics previously used and many others have been examined in the present study: leaf and bract size, shape, dentation, and pubescence; petal size and shape; size of pollen grains and stomata; size of seeds and length of tubercles thereon. Special attention has been given to frequency of plantlet production since this is a prime diagnostic feature in existing classifications. The many morphological features examined have all been found to vary so much even within populations that no pattern of subspeciation has appeared.The conclusion is that S. ferruginea should be considered one variable species, there being no stable characters and correlated differences on which to base subcategories. A summary of the reproductive cycle of the species is included.

THE INDEPENDENT ANEUPLOID ORIGIN OF TWO SPECIES OFCHAENACTIS(COMPOSITAE) FROM A COMMON ANCESTOR

Very similar species are of great interest to students of evolution because such species probably have evolved recently, making it likely that much of the evidence of their origin can be reconstructed. In very few instances of closely similar non-polyploid plant species is there evidence to suggest that one is the ancestor of another. A notable example is the cytological evidence for the origin of Crepis fuliginosa (n-= 3) from C. neglecta (n = 4) or its near ancestor (Tobgy, 1943). Similarly, Sherman (1946) showed that Crepis kotschyana (n = 4) has been derived from an ancestor like C. foetida (n 5). Another convincing example of an aneuploid species with a living diploid ancestor was described by Lewis and Roberts (1956) in their studies of Clarkia biloba (n= 8) and C. lingulata (n -9). These two species are so similar that they can only be distinguished by petal shape and chromosome number. Cytogenetic analysis showed that C. lingulata has an additional chromosome composed of parts of two chromosomes of the C. biloba genome. The presence of duplicated chromosome material in C. lingulata clearly establishes it as a derivative of C. biloba. Recently, Jackson (1962) described a case in Haplopappus that also suggests the origin of one diploid species from another. What was considered Haplopappus gracilis was found to consist of two extremely similar species, one with a chromosome number of n = 4, the other with n = 2. Cytological evidence indicates in this instance, as in Crepis, that aneuploid reduction is the most probable explanation for the difference in chromosome number, with the n = 2 species the derived one. The purpose of this paper is to present a unique example in Chaenactis (Compositae) in which the cytogenetical evidence indicates beyond reasonable doubt that an extant species of relatively mesic habitats, C. glabriuscula DC., has given rise independently to two similar desert species, C. fremontii Gray, and C. stevioides H. & A., by aneuploid reduction in chromosome number. Chaenactis comprises approximately 24 herbaceous species, all endemic to western North America. There are at least nine annual species, and four of these, C. glabriuscula, C. stevioides, C. fremontii, and C. xantiana form a closely related assemblage,2 judging from their similarity and frequent natural hybridization. The first three will be considered in detail in this paper. The yellow-flowered C. glabriuscula is the most variable, and some of its intergrading variants have been treated as separate species.3 Chaenactis stevioides and C. fremontii have white flowers, but are otherwise very similar morphologically to certain populations of C. glabriuscula. Despite their overall similarity, the gametic chromosome number of C. glabrius-

CHROMOSOMAL REPATTERNING INCLARKIA RHOMBOIDEAAS EVIDENCE FOR POST-PLEISTOCENE CHANGES IN DISTRIBUTION

Clarkia rhomboidea Douglas (Onagraceae) is a widely distributed western North American annual of polyploid origin (Lewis and Lewis, 1955; Mosquin, 1961). Studies of meiotic associations of chromosomes in artificial interpopulational hybrids of this species indicate that since its origin a considerable amount of chromosomal reorganization has occurred among natural populations. The chromosomes have been altered both by reciprocal translocations and paracentric inversions. The purpose of this paper is to examine the evidence for the origin of C. rhomboidea and to determine the subsequent course of chromosomal differentiation in this species. When considered together with the recent climatic history of the western United States, the cytogenetic information provides unusual clues to the recent changes in distribution pattern and paths of migration followed by C. rhomboidea since its origin. Clarkia rhomboidea ranges from the mountains of southern California northward in a broad belt following the Sierra Nevada, the Coast Ranges, and the Cascade Range to Washington and extends eastward into Idaho. Widely disjunct populations occur in Utah and Arizona. The species is absent from the southwestern deserts and the arid interior of Oregon and Washington (fig. 1). The populations are adapted to a wide range of habitats. In Arizona, Utah, Nevada, and most of California they occur in the broad transition zone between the Arcto-Tertiary and the Madro-Tertiary Geofloras associated usually with yellow pine (Pinus ponderosa) and various oaks. However, from the higher elevations of the Sierra Nevada in California to the northern limits of the species range, the colonies are generally found in coniferous or montane forest. The wide range of ecological tolerance is especially evident on the western slopes of the Sierra Nevada of California where populations occur from the mesic margins of montane meadows at 10,000 feet elevation to the arid oak woodland and chaparral associations at about 1,800 feet. Plants of this species tend to be colonial with populations varying in size from a few individuals to many hundreds. However, single plants and small colonies often occur sporadically over many miles of favorable terrain. Herbarium specimens as well as field and garden observations indicate that interpopulational variation is especially pronounced in this species (Lewis and Lewis, 1955; Mosquin, 1961). The most conspicuous variables are flowering time, habit, leaf and petal shape, and flower size. With respect to breeding habit, populations with small flowers are automatic selfers whereas those with larger flowers tend to be outcrossed. The chief pollinators are various Hymenoptera. The plants are self-compatible and capsules of most plants set a full complement of seed when isolated from insects. As in other species of Clarkia, the seeds have no mechanism for longrange dispersal and are as a rule dropped near the parent plant. The chromosome number in C. rhomboidea is n = 12 and is based upon an examination of 74 plants from 47 populations 1 This investigation was carried out while the writer was a graduate student at the Department of Botany, University of California, Los Angeles, and is a portion of a dissertation submitted as part of the requirements for the degree of Doctor of PhilosoDhv.

THE COMPARATIVE BIOLOGY OF CLOSELY RELATED SPECIES LIVING IN THE SAME AREA

SummaryThe morphology of Papaver dubium and P. lecoqii are contrasted. The colour of latex, leaf dissection, petal shape and height of stamens are considered good characters for distinguishing between them. The shape of the capsule and stigmatic disc are considered unreliable taxonomic characters.Experimental cross‐pollinations show that the species can produce hybrids readily, that the hybrid seed germinates with little or no dormancy, to give plants showing some degree of hybrid vigour but morphological characters intermediate between the parents. The F1 hybrids show very severely reduced fertility, but this is rapidly restored in many of the F2 and backcross progeny.Naturally occurring hybrids have not been found, and there are problems in the way of recognizing them and proving their hybrid nature if they do occur.The continued coexistence of these two species without merging of their specific characters is made possible by barriers to gene flow occurring at three levels of organization: (a) ability of the parents to set seed by selfing, (b) ill‐adapted hybrids and (c) infertility of the F1 generation.

A SINGLE FACTOR MUTATION IN MELILOTUS ALBA DESC. HAVING MULTIPLE EFFECTS ON HOMOLOGOUS STRUCTURES

The multiple effect of a single factor mutation in Melilotus alba which affects several diverse characters of the plant including shape of leaflets and petals, position of the staminal column, morphology of the pistil, female fertility and vigor of growth, is described.The results are significant in showing that one of the genes which presumably determined leaf shape in the species ancestor still continues to modify the shape of those organs which have evolved from the leaf.