Symmetry is an important floral character and is often associated with the degree of pollination specialization. Typically floral symmetry is fixed within a species. Rotational symmetry occurs in two different corolla variations according to the direction in which the petals overlap. This study describes the pattern of polymorphism in corolla chirality of Hypericum irazuense Kuntze ex. N. Robson and H. costaricense N. Robson. The individuals of these species exhibit flowers with corollas that rotate either counter clockwise (left/sinistrorse) or clockwise (right/dextrorse). Studying this pattern of floral expression is the first step in gaining a better understanding of whether this trait polymorphism is maintained due to an adaptive advantage or as a byproduct of a developmental genetic constraint. We quantified the proportion of dextrorse and sinistrorse flowers for H. irazuense and H. costaricense. We also examined whether the chirality of a flower is independent of the corolla chirality of its neighbor flower at the ultimate branch level, i.e., a group of terminal branches that are connected by the same node. We demonstrate that the proportion of sinistrorse and dextrose flowers is equal among individuals within a population of H. irazuense and H. costaricense. In addition, we show that in these populations, the forms are randomly distributed at the ultimate branch level indicating that the identity of a flower type is not determined by the chirality type of its neighbor flower. The 1∶1 proportion of chirality types among individuals suggests that the maintenance of both flower forms may convey a reproductive benefit. But, the random distribution of flower type at the ultimate branch level challenges this interpretation. Further studies are needed to address the adaptive significance, if any, of this pattern of dextrorse and sinistrorse flowers.

The species chosen in this study were Aldama filifolia (Sch. Bip. ex Baker) E.E.Schill. & Panero, A. linearifolia (Chodat) E.E.Schill. & Panero, and A. trichophylla (Dusén) Magenta, which are morphologically very similar. Their representatives are perennial, cespitose herbs with an odoriferous resin and a xylopodium with tuberous adventitious roots. These species are from Cerrado areas and present seasonality of development. The aim of the present study was to provide anatomical features of the underground system of the aforementioned species and try to explain certain aspects of their environmental adaptation. Some of the structural characteristics observed in the Aldama species are new for the Asteraceae family, such as a secondary protective tissue similar to storied cork, the variation of cambial activity in A. filifolia, and the tuberisation process by division of the medullary parenchyma cells. The essential oil composition of the xylopodia and roots showed some differences among the species and allowed the identification of some compounds with biological properties. The underground system, which has gemmiferous ability and tuberised roots able to store inulin-type fructans, is related to the seasonality of growth and the adaptation of such plants to the environmental conditions of their habitat.

This paper mainly studies the formation and development of the rhizoids of Marchantia polymorpha L. using light and electron microscopy, and cytochemical methods. Marchantia polymorpha has highly specialized rhizoids that can be divided into two types, namely, tuberculate rhizoids and smooth-walled rhizoids. Tuberculate rhizoids individually originate from the lower superficial cells of the apical meristem. Obvious tubercles exist in the lumen of rhizoids, which always lie parallel to the thallus surface and converge toward the midrib. Smooth-walled rhizoids always exist in clusters in free portions near the midrib in the posterior of the thallus. These smooth rhizoids always grow toward moist soil and lie perpendicular to the thallus surface. Developmental observations show that the initial cell of a tuberculate rhizoid that arises from the lower epidermis possesses a dense cytoplasm. The rapid polar growth of a rhizoid produces a non-pigmented tubular cell. A growing rhizoid possesses an apical cytoplasmic mass, which contains numerous vesicles, Golgi bodies, and peripheral endoplasmic reticula. The nucleus always follows the apical cytoplasmic mass. The remainder of the cytoplasm located behind the nucleus appears to undergo a degeneration process. Simultaneously, a tuberculate wall is formed by the deposition of fibrillar materials onto the inner side of the primary wall. Histochemical investigation shows that the wall of the rhizoid is polysaccharide in nature and most likely contains callose that accounts for their fluorescence property upon staining with Aniline Blue. The base of a smooth-walled rhizoid has small tuberculated projections; however, the wall of the anterior part of the rhizoid is always smooth.

The regeneration of temperate forests is important, especially for those located in urban areas. Sources of propagules, such as seed rain, shape the structure and composition of systems where the availability of diaspores from forest species contribute to both local biodiversity and ecosystem services; these elements are crucial in Mexico City. Over the course of one year, we estimated natural regeneration potential through an analysis of the seed rain deposited in traps that were placed at soil level in plots in three vegetation types: oak, fir and pine forests. We addressed the following questions: Do abundance, density, species composition and diversity of seed rain differ among vegetation types and seasons? How similar is the seed rain to the standing vegetation? Is seed rain a potential source for the natural regeneration of temperate forests? The results showed that the abundance and density of seeds were significantly higher for oak and fir forests due to a higher number of herb, shrub, and tree species in the standing vegetation. The most abundant species in the total seed rain was Ageratina enixa (B.L. Rob.) R.M. King & H. Rob. (12%), but inside individual forest plots, the most abundant were Quercus rugosa Née (16%), Abies religiosa (Kunth) Schltdl. & Cham. (17.5%) and Pinus hartwegii Lindl. (41%). Diversity index values differed among vegetation types but not seasons. Most diaspores in the seed rain corresponded to native species (97%). The similarity between seed rain and the standing vegetation was 40%. In total, 62% of the species are anemochorous, as a result of the high number of Asteraceae species present, and endozoochory is the second most important (17%) dispersal syndrome. A slight asynchrony was observed between the peaks of anemochorous and zoochorous species.

Coarse woody debris (CWD) provides vital habitat and resources for a broad variety of organisms in old-growth stands. Although many studies have quantified CWD, it remains unclear how variability in tree species composition relates to CWD and snag volume. If CWD and snags (standing dead trees) vary substantially with tree species abundance among different forest types, then the volume of CWD may change in response to shifts in tree species composition. Dominant canopy tree species vary significantly in their decay resistance, shade tolerance, and suppression of light transmission through the canopy; therefore, the rate of CWD input and output may vary with dominant tree species abundance. We hypothesize that CWD and snag volumes are positively related to the abundance of late-successional shade-tolerant canopy species and negatively related to the abundance of mid-successional oak species. To test this hypothesis, CWD was surveyed in 18 late-successional and mature stands across three physiographic provinces in Pennsylvania. The stands were classified by composition: ten as red oak-mixed hardwood and eight as hemlock-mixed hardwood. The hemlock-mixed hardwood stands (vs. the oak-mixed hardwood stands) had larger volumes of CWD and higher relative abundance of shade-tolerant species. CWD volume was positively correlated with the basal area of hemlock and all shade-tolerant species combined. In contrast, basal area of oak species was negatively correlated with the volume of snags and CWD. These results supported the hypothesis that CWD volume is greater in stands dominated by late-successional species, particularly hemlock, than in stands dominated by oak species. The volume of CWD did not change significantly with the abundance of any other tree species (e.g., red maple (Acer rubrum L.), beech (Fagus grandifolia Ehrh.)). Understanding the relationship between tree species composition and the volume of CWD and snags can provide insight into future CWD characteristics as pathogens dramatically change eastern forests (e.g., beech bark disease, hemlock woolly adelgid).

Fruits and seeds of the genus Chenopodium have been considered taxonomically important but have not been fully studied or utilized. We discuss the importance of describing fruit and seed morphology at low magnification to improve the identification and taxonomy of North American taxa of Chenopodium, which in a large part remains unresolved. A new species, Chenopodium nitens Benet-Pierce & M. G. Simpson, is described, integrating these reproductive characters with general vegetative characters.

Field expeditions carried out in three biologically important localities in the semi-arid region of Brazil revealed four new species for the genus Cyathus: C. calvescens R. Cruz & Baseia, C. hortensis R. Cruz & Baseia, C. magnomuralis R. Cruz & Baseia, and C. parvocinereus R. Cruz & Baseia. Taxonomic data are presented as descriptions of species, commentaries, photos and illustrations of basidiomata.

This paper describes Plantago corvensis, a new species endemic to rocky cliffs in Serra do Corvo Branco, southern Santa Catarina, southern Brazil. The new species is morphologically very distinct from other Plantago species native to South America because of the distinctly petiolate ovate leaves, the retrorse trichomes on scape, and the 4-seeded fruits. Plantago corvensis is known from only one locality and, according to the IUCN criteria, is considered critically endangered (CR).