Axillary Inflorescences Research Articles

Miliusa microphylla (Annonaceae), a new species from Thailand as evidenced by morphology and plastid phylogeny, with M. glandulifera, a new record for Thailand

On the basis of expansive molecular phylogenetic analyses of the genus Miliusa (Annonaceae) utilising up to seven plastid DNA regions, four major clades are identified: clades A, B, C and D. Members of clade C possess axillary inflorescences and crescent-shaped to semicircular glandular structures at the base or (slightly) higher inside the inner petals. In this clade, accessions of M. mollis are recovered as a monophyletic group, divided into two major clades. One of them is recognised as a new species, M. microphylla, which differs from the other (M. mollis) in the following characters: pedicel length, as well as glandular structures and indumentum on the inner petals. The new species is endemic to southeastern Thailand, whereas M. mollis has a much wider distribution (central, eastern, northeastern, northern and peninsular Thailand plus Cambodia and Vietnam). In addition, M. glandulifera, a new record for Thailand, is retrieved as the sister group of a clade composed of M. microphylla and M. mollis. The name M. glandulifera is lectotypified and the description of M. glandulifera is emended, with the information on mature monocarps added. The conservation status of M. microphylla and M. glandulifera is provisionally assessed. A revised key to the species in clade C in Thailand is provided. The phylogenetic position of M. nakhonsiana and M. sessilis in clade C, as well as of M. chantaburiana and M. eupoda in clade B is confirmed for the first time.

Untangling inflorescences in Miconieae (Melastomataceae): development, typology, and the systematic and evolutionary implications.

This study aimed to describe the origin, position, development and typology of inflorescences in Miconieae through ontogenetic and morphological analyses using light microscopy. We observed three morphological character states: terminal, pseudo-axillary and axillary; and two ontogenetic states: terminal and axillary. The terminal and pseudoaxillary inflorescences originate from terminal reproductive meristems. Pseudoaxillary inflorescences result from unequal development of vegetative meristems which flank the terminal flowering unit, whereas in terminal inflorescences, both vegetative meristems develop equally. In axillary inflorescences, the terminal reproductive meristem is not involved, while axillary inflorescences originate from reproductive axillary meristems. The inflorescences range from heterocladic and thyrsoid to simpler types, such as botryoid and triad. Such characteristics can also be seen in paracladia, particularly those most distal. The terminal inflorescence is observed in all clades of Miconieae, and pseudoaxillary and axillary inflorescences should be apomorphic states in the tribe and derived from the terminal condition.

Transcriptomic Analysis of the Pistacia vera (L.) Fruits Enable the Identification of Genes and Hormone-Related Gene Linked to Inflorescence Bud Abscission.

Pistacia vera (L.) is an alternate bearing species. The tree produces axillary inflorescence buds every year. Still, they abscise in “ON” overloaded shoots, causing a limited production in the following “OFF” year, causing a significant and unfavorable production fluctuation. In this work, we carried out de novo discovery and transcriptomic analysis in fruits of “ON” and “OFF” shoots of the cultivar Bianca. We also investigated whether the fruit signaling pathway and hormone biosynthesis directly or indirectly linked to the premature fall of the inflorescence buds causing alternate bearing. We identified 1536 differentially expressed genes (DEGs) in fruits of “ON” vs. “OFF” shoots, which are involved primarily in sugar metabolism, plant hormone pathways and transcription factors. The premature bud abscission linked to the phenomenon is attributable to a lack of nutrients (primarily sugar) and the possible competition between the same branches’ sinks (fruits vs. inflorescence buds). Hormone pathways are involved as a response to signals degradation and remobilization of carbon and nutrients due to the strengthening of the developing embryos. Genes of the secondary metabolism and transcription factors are also involved in tailoring the individual branches response to the nutritional stress and sink competition. Crosstalk among sugar and various hormone-related genes, e.g., ethylene, auxin, ABA and cytokinin, were determined. The discovery of putative biomarkers like callose synthase 5, trehalose-6-phosphate synthase, NAD(P)-linked oxidoreductase and MIOX2, Jasmonate, and salicylic acid-related genes can help to design precision farming practices to mitigate the alternate bearing phenomenon to increase farming profitability. The aim of the analysis is to provide insight into the gene expression profiling of the fate of “ON” and “OFF” fruits associated with the alternate bearing in the pistachio.

Pyramidanthe and Mitrella (Annonaceae, Uvarieae) unified: molecular phylogenetic and morphological congruence, with new combinations in Pyramidanthe

The delimitation of the genera Pyramidanthe and Mitrella in the tribe Uvarieae of the family Annonaceae is assessed by molecular phylogenetic analyses and morphological re-evaluation. Using up to six plastid DNA regions (matK, ndhF, rbcL exons; trnL intron; psbA-trnH, trnL-trnF intergenic spacers) and including, among others, two accessions of Pyramidanthe and five accessions of Mitrella, the resulting phylogeny shows that Pyramidanthe and Mitrella are recovered in a clade sister to the Fissistigma clade. The Pyramidanthe-Mitrella clade is composed of a trichotomy: a clade consisting of Pyramidanthe accessions and two clades containing Mitrella accessions. In combination with negligible morphological distinctions between the two genera, they are consequently merged, with 11 new combinations under the chosen name Pyramidanthe: P. beccarii, P. clementis, P. cylindrica, P. dielsii, P. elegans, P. kentii, P. ledermannii, P. mabiformis, P. schlechteri, P. sylvatica and P. tiwiensis. The names M. dielsii (the basionym of P. dielsii) and P. rufa (a heterotypic synonym of P. prismatica) are lectotypified. Pyramidanthe s. lat. possesses the following diagnostic traits: usually indistinct secondary leaf veins with a brochidodromous to brochidodromous-eucamptodromous venation, a reticulate tertiary leaf venation, axillary inflorescences, presence of a basal excavation on an inner side of each outer petal, and inner petals that are much smaller than the outer petals and cohering marginally at anthesis. Citation: Bangkomnate R., Damthongdee A., Baka A., Aongyong K. & Chaowasku T. 2021: Pyramidanthe and Mitrella (Annonaceae, Uvarieae) unified: molecular phylogenetic and morphological congruence, with new combinations in Pyramidanthe. – Willdenowia 51: 383–394. Version of record first published online on xx December 2021 ahead of inclusion in December 2021 issue.

Interactions between SQUAMOSA and SHORT VEGETATIVE PHASE MADS-box proteins regulate meristem transitions during wheat spike development.

Inflorescence architecture is an important determinant of crop productivity. The number of spikelets produced by the wheat inflorescence meristem (IM) before its transition to a terminal spikelet (TS) influences the maximum number of grains per spike. Wheat MADS-box genes VERNALIZATION 1 (VRN1) and FRUITFULL 2 (FUL2) (in the SQUAMOSA-clade) are essential to promote the transition from IM to TS and for spikelet development. Here we show that SQUAMOSA genes contribute to spikelet identity by repressing MADS-box genes VEGETATIVE TO REPRODUCTIVE TRANSITION 2 (VRT2), SHORT VEGETATIVE PHASE 1 (SVP1), and SVP3 in the SVP clade. Constitutive expression of VRT2 resulted in leafy glumes and lemmas, reversion of spikelets to spikes, and downregulation of MADS-box genes involved in floret development, whereas the vrt2 mutant reduced vegetative characteristics in spikelets of squamosa mutants. Interestingly, the vrt2 svp1 mutant showed similar phenotypes to squamosa mutants regarding heading time, plant height, and spikelets per spike, but it exhibited unusual axillary inflorescences in the elongating stem. We propose that SQUAMOSA–SVP interactions are important to promote heading, formation of the TS, and stem elongation during the early reproductive phase, and that downregulation of SVP genes is then necessary for normal spikelet and floral development. Manipulating SVP and SQUAMOSA genes can contribute to engineering spike architectures with improved productivity.

Integrative analysis of HD-Zip III gene PmHB1 contribute to the plant architecture in Prunus mume

Mei (Prunus mume) is a traditional fruit and ornamental woody plant. P. mume cultivars with dwarf and dense intersecting branched tree architecture are essential for enhancing the ornamental value and application diversity, such as bonsai, flower arrangement and potted plants. However, little is known about the mechanism of branching in P. mume. The apical meristem produces the organs of the above-ground part, which is essential for branch development. The HD-Zip III subfamily transcription factors influence the development of multiple lateral organs and meristem maintenance. However, their roles in regulating tree architecture have not been studied in P. mume. Here, the PmHB1 gene, encoding the HD-Zip III subfamily transcription factor, was strongly expressed in the hypocotyl, young leaf, root primordia, leaf bud, flower bud, style, and vascular tissues in leaf and inflorescence, which could respond to multiple plant hormones (such as GA3, IAA, ZA, KT, and BR). It is worth noting that there was a significant correlation between branch quantity and PmHB1 expression level in different mei cultivars. The formation of PmHB1 protein was controlled through the miR165/166 post-transcriptional regulation. Overexpression of the PmHB1 gene in Arabidopsis increased of the number of primary axillary inflorescence in leaf axil and secondary axillary inflorescence in the cauline leaf axil. The expression levels of genes involved in meristem maintenance (CLV3, RAP2.6 L, STM, BEL1, PEAR, WUS), auxin metabolism and signal transduction (IAA30, IAA20, PIN1, LAX3, LAX2, YUCCA5, TAA1, MP), cytokinin metabolism, and signaling transduction (IPT4, IPT7, ARR1, ARR2, MET1) were significantly changed in transgenic Arabidopsis. Moreover, according to yeast two-hybrid and bimolecular fluorescence complementation experiments, the transcription factor PmHB1 could interact with multiple proteins, such as Pm005033 (PmCSN5A), Pm005297 (PmHSFB4), Pm016138 (PmSPL13A), Pm024774 (PmEB1A), and Pm026192 (PmZPR4). Taken together, the PmHB1 gene could regulate the apical meristem development and promote the branching in P. mume.

Phylogeny, classification, and character evolution of tribe Citharexyleae (Verbenaceae).

As a family of Neotropical origin and primarily Neotropical distribution, the Verbenaceae are a good but understudied system with which to understand Neotropical evolution. Tribe Citharexyleae comprises three genera: Baillonia, Citharexylum-one of the largest genera in Verbenaceae-and Rehdera. A molecular phylogenetic approach was taken to resolve intergeneric relationships in Citharexyleae and infrageneric relationships in Citharexylum. The phylogeny is used to elucidate character evolution in a widespread, morphologically diverse Neotropical genus. Seven plastid regions, two nuclear ribosomal spacers, and six low-copy nuclear loci were analyzed for 64 species of Citharexyleae. Phylogenetic analyses were conducted using maximum likelihood, Bayesian inference, and multispecies coalescent approaches. Habit, presence or absence of thorns, inflorescence architecture, flower color, fruit color, and geography were examined to identify diagnostic character states for clades within Citharexylum. Rehdera is resolved as sister to Citharexylum, and Baillonia nested within Citharexylum. Two species, C. oleinum and C. tetramerum, are not closely related to tribe Citharexyleae, but may be related to members of tribe Duranteae instead. Seven clades within Citharexylum are inferred, each characterized by a combination of geography, fruit color and/or maturation, and inflorescence architecture. There is evidence of correlated evolution between habit, axillary inflorescences, and flower number per inflorescence. Shrubs with reduced inflorescences have evolved repeatedly. A subgeneric classification for Citharexylum is proposed. Although suites of associated traits are found, character morphology has been labile throughout Citharexylum's evolutionary history. Morphological diversity may be related to adaptation to differing mesic and xeric habitats.

Monograph and Molecular Phylogeny of the Mexican Endemic Lasiocarpus (Malpighiaceae) Reveal a New Species for Southern Mexico

Abstract— Lasiocarpus is a genus of bisexual, dioecious, or trioecious shrubs or small trees of Malpighiaceae endemic to the seasonally dry tropical forests of the Pacific slopes of Mexico. In this paper the monophyly of this genus is tested using a molecular phylogeny based on three plastid (ndhF, matK, rbcL) and a single nuclear (PHYC) markers that were newly sequenced for the three currently accepted species in this genus, along with representative taxa from the main phylogenetic groups previously recognized in Malpighiaceae. The three species of Lasiocarpus were retrieved in a well supported clade corroborating the monophyly of this genus. A taxonomic treatment of this genus is presented. Lasiocarpus ovalifolius is synonymized with L. salicifolius, and a new species, Lasiocarpus andersoniorum, endemic to Southern Mexico, is proposed. It is morphologically distinguished by characters such as axillary inflorescences, reflexed sepals, petals with crenate margin and strigose indumentum, large styles, and 2-lobed stigmas. The taxonomic revision includes morphological descriptions and distribution maps for the three accepted species of Lasiocarpus.

Two new species of Begonia (sect. Platycentrum, Begoniaceae) from the Central Highlands of Vietnam: B. villosula and B. lophura

Two new species of Begonia L., namely Begonia villosula T.S.Hoang & C.W.Lin and B. lophura T.S.Hoang & C.W.Lin, from the Central Highlands of Vietnam, are described and illustrated. They are assigned to Begonia sect. Platycentrum based on several characters including axillary inflorescence, 4-tepaled staminate flower and 5-tepaled pistillate flower with bilocular ovary, each with two placentae. Begonia villosula resembles B. thomsonii, but it is different in its leaf margins crenate to crenulate (vs. irregularly serrulate), stamens 80–120 (vs. 35–70), pistillate flower 4-tepaled (vs. 5-tepaled) and ovary hirsute (vs. villous). Begonia lophura is somewhat similar to B. pavonina, but it is different in having widely ovate (vs. ovate) and abaxially red hirsute (vs. glabrous) leaves, bracts persistent (vs. caducous), tepals hirsute (vs. glabrous) in both of staminate and pistillate flowers, capsule scabrous (vs. glabrous) and abaxial wing strongly swollen (vs. thin, not swollen). The conservation status of the two new species are assessed as Vulnerable according to the IUCN Red List criteria.

Changes of Growth and Inflorescence Initiation by Exogenous Gibberellic Acid3 and 6-Benzylaminopurine Application in Phalaenopsis Orchids

This study was conducted to observe the effects of exogenous gibberellic acid3 (GA3) and 6-benzylaminopurine (BAP) treatments on the growth and inflorescence initiation of Phalaenopsis and to determine whether hormonal applications can substitute for low-temperature exposure for floral transition. Phalaenopsis Queen Beer ‘Mantefon’ clones were treated with no hormones (control), GA3 100 mg/L, GA3 200 mg/L, BAP 100 mg/L, and GA3 100 mg/L + BAP 100 mg/L by foliar spray. The treatments were carried at 28 °C for vegetative growth and 20 °C for forcing, respectively. At 28 °C of vegetative temperature, all exogenous hormonal treatments did not induce inflorescence initiation, but lateral shoots were observed in BAP-treated plants even though this plant is a monopodial orchid. GA3 significantly increased leaf length and decreased leaf width, and consequently increased length:width (L:W) ratio compared with the control and BAP alone. The trend grew as GA3 concentration increased. Also, the GA3 increased stem length and decreased stem diameter. At 20 °C of forcing temperature, L:W ratio responded similarly to 28 °C in GA3 treatments, but leaf size was smaller than for the control or BAP alone. BAP accelerated inflorescence emergence and significantly increased inflorescence numbers, whereas GA3 and GA3 + BAP slightly delayed inflorescence emergence. GA3 significantly promoted new leaf development at 20 °C of forcing condition. These results indicated that cytokinin was associated with the break of axillary vegetative and inflorescence meristems and exogenous GA3 spray did not improve inflorescence initiation in Phalaenopsis. Although exogenous hormonal application did not substitute for low-temperature exposure, it showed a possibility in promoting the growth and inflorescence initiation.

A review of the classification and taxonomic and geographic distribution of cleistogamy in Australian grasses

Cleistogamy, self-fertilisation within a closed flower, was found in 135 Australian grass species from 46 genera within 5 subfamilies representing 14% of the species and 30% of the genera. This represents an increase from 4% of species and 12% of genera from previous records. Expressions of cleistogamy were classified into three main categories on the basis of: presence or absence of anther dimorphism, presence of amphigamy with or without spikelet peculiarities, and chasmogamous and cleistogamous spikelets on separate plants. One category of these dimorphisms involves species that have differing terminal and axillary inflorescences (amphigamy) with corresponding spikelets so different that the axillary ones appear to belong to a different genus. Dimorphisms within cleistogamous species were found in inflorescences, spikelets, florets, anthers and caryopses. The highest concentration of Australian cleistogamous grasses occurs in the subtropical climatic zone and more than three-quarters of the species are chloridoid and panicoid with nearly equal proportions. Of Australian cleistogamous grasses, 33% have C3 photosynthetic pathway and 67% have C4, and the largest taxonomic groups are panicoid with 38% and chloridoid with 39%.

Inflorescence Position Influences Phenological Rhythms in Leguminosae Species

Abstract We present a case study focusing on the influence of inflorescence position on the relationships between foliar and reproductive phases, focusing on three Leguminoseae tree species in the Chapada Diamantina, Brazil. Both Senna multijuga and Copaifera langsdorffii produce terminal panicles and showed vegetative and reproductive phenophases that were correlated but segregated in time, with the marked concentration of reproductive data. The presence of axillary inflorescences on Inga cayennensis enables the simultaneous production of both flowers and leaves, without the segregation or the correlation of those phases, with a uniform distribution of reproductive data. This study encourages further investigations regarding the effects of inflorescence position on plant phenology.

Aspectos reproductivos, arquitectura y fenomorfología de Maytenus boaria Molina (Celastraceae) en Chile central

Maytenus boaria Molina (Celastraceae) is an evergreen native tree which is widely distributed in Chile. It has a high economic potential due to its medicinal value, among others. Despite this, biological information about the species is scarce and often confusing. The objective of the study was to broaden the knowledge about reproductive aspects and the sexual system of M. boaria, along with its modular architecture and pheno-morphology. The study was conducted from August through December of 2016, with adults plants (n=17) selected in urban areas of the Region Metropolitana. A pollination test was performed and the sex of the flowers of each selected tree was identified. In addition, a pheno-morphological diagram of the species was made through the modular interpretation of its architecture and the identification of its phenophases. Results showed that M. boaria is a dioecious and andromonoecious species; it has a low autonomous autogamy and is non-apomictic species that needs pollination vectors for seed production. It has four architectural modules in its crown: dolichoblast of apical bud, dolichoblast of axillary bud, inflorescence and reproductive temporary brachyblasts which are distributed in two architectonic units. The floral biology and pheno-morphology of this species indicate that it would be in an evolutionary process regarding the functionality of hermaphroditic flowers, which has been proposed as an intermediate step from hermaphroditism to dioecy. Further knowledge of these topics will allow for a better understanding of the autoecology of the species in order to have an appropriate and productive management of it.

Description of a new natural Sonneratia hybrid from Hainan Island, China

Here, we describe, illustrate and compare a new natural hybrid, Sonneratia × zhongcairongii Y. S. Wang & S. H. Shi (Sonneratiaceae), with its possible parent species. Based on its morphological characteristics and habitat conditions, this taxon is considered to represent a sterile hybrid between S. alba and S. apetala. In China, the new hybrid is only reported in the mangrove forest in Dongzhai Harbour, Hainan Island. It has intermediate characteristics with its parents by elliptical leaf blades, peltate stigma, terminal or axillary inflorescence with 1–3 flower dichasia, cup – shaped calyx (4–6 calyx lobes) and no petals. We also provide a key for the identification of Sonneratia species.

Bredia reniformis (Melastomataceae), a new species from Guangxi, China

Bredia reniformis, a new species of Melastomataceae from Guangxi, China, is described and illustrated. Bredia reniformis is similar to B. plagiopetala (C. Chen) R. C. Zhou & Ying Liu and B. gracilis (Hand.‐Mazz.) Diels by having axillary inflorescences and flowers with eight isomorphic stamens, but differs from the latter two in having glandular‐puberulous indumentum, reniform calyx lobes and shortly falcate yellowish anthers with obconical dorsal appendages.

From Polyalthia to Polyalthiopsis (Annonaceae): transfer of species enlarges a previously monotypic genus.

The genus Polyalthiopsis Chaowasku (Annonaceae) was a poorly known monotypic genus from Vietnam that was recently segregated from the highly polyphyletic genus Polyalthia s.l. The sister clade relationship between Polyalthiopsis and Miliusa was not well established in previous study. The phylogenetic position of two Polyalthia spp. from China, P. chinensis S.K.Wu ex P.T.Li and P. verrucipes C.Y.Wu ex P.T.Li, remains unresolved and is shown here to be phylogenetically affiliated with Polyalthiopsis. Phylogenetic analyses of six chloroplast regions (matK, ndhF, psbA-trnH, rbcL, trnL-F and ycf1; ca.7.3 kb, 60 accessions) unambiguously placed Polyalthia chinensis and P. verrucipes in the same clade with Polyalthiopsis floribunda (PP = 1, MPBS = 97%); the entire clade is sister to Miliusa with weak to strong support (PP = 1, MPBS = 54%). Polyalthia chinensis and P. verrucipes share several diagnostic characters with Polyalthiopsis floribunda, including the raised midrib on the upper surface of the leaf in vivo, conspicuous foliar glands when dried, petiole with transverse striations when dried and axillary inflorescences. The two species differ from Polyalthiopsis floribunda in having fewer flowers per inflorescence, longer linear petals and two ovules per carpel. On the basis of the combined molecular phylogenetic and morphological data, we propose two new combinations, Polyalthiopsis chinensis (S.K.Wu ex P.T.Li) B.Xue & Y.H.Tan and Polyalthiopsis verrucipes (C.Y.Wu ex P.T.Li) B.Xue & Y.H.Tan. The protologue of Polyalthia verrucipes did not include a description of the flowers, which we provide here. An updated description for the genus Polyalthiopsis and a key to species in the genus Polyalthiopsis is also provided.

A New Species of Justicia (Acanthaceae: Acanthoideae: Justicieae) from Northeastern Brazil

Abstract—Justicia rubrobracteata, a new species from northeastern Brazil, is described and illustrated. The new species is morphologically similar to J. aequilabris due to its shrubby habit, and terminal and axillary spicate inflorescences with red flowers. However, J. rubrobracteata is differentiated mainly by the shape and color of its bracts and bracteoles as well as an orangish macula in the corolla, and a torulose capsule. In addition, J. rubrobracteata is only known from northeastern Brazil, from the states of Paraíba and Rio Grande do Norte, while J. aequilabris is widely distributed in Bolivia, Brazil, and Paraguay. A table with the main morphological characters of both species is included, as well as photographs, a key to species of Justicia for the states of Paraíba and Rio Grande do Norte in northeastern Brazil, a distribution map of both species, and conservation data for the new species.

I am all ears: Maximize maize doubled haploid success by promoting axillary branch elongation.

The maize doubled haploid (DH) technology plays an important role in accelerating breeding genetic gain. One major challenge in fully leveraging the potential of DH technology to accelerate genetic gain is obtaining a consistent seed return from haploid (DH0) plants after chromosome doubling. Here we demonstrated that DH0 seed production can be increased by increasing the number of mature axillary female inflorescences (ears) at anthesis. To determine the maximum capacity of a maize plant to develop ears, we first characterized the developmental progression of every axillary meristem. We found that all axillary meristems developed to a similar developmental stage before the reproductive transition of the shoot apical meristem (SAM). Upon reproductive transition of the SAM, all axillary meristems are released for reproductive development into ears in a developmental gradient reflective on their positions along the main stem. However, under most circumstances only the top one or two ears can generate silks at anthesis. We found that applying the GA inhibitor paclobutrazol (PAC) during the early reproductive transition of axillary meristems increased the number of silking ears at anthesis, leading to increased success of self‐pollination and seed production. These results provide a blueprint to improve DH efficiency and demonstrate the potential of breeding innovation through understanding crops’ developmental processes.

<p><strong><em>Perakanthus longipetalus </em></strong><strong>(Rubiaceae), a new combination, and the first record of the genus outside Peninsular Malaysia</strong></p>

Canthium longipetalum Y.H.Tan & S.S.Zhou in Yang et al. (2019: 197) is a species of Rubiaceae recently described from northern Myanmar. This species was identified as belonging to the Vanguerieae tribe, and was placed provisionally in the genus Canthium Lamarck (1783: 602) based on morphological characters including the presence of axillary inflorescences, valvate corolla aestivation, two-locular ovaries, and a two-lobed stigma (Yang et al. 2019). However, the suite of characters cited by the authors to support the placement of their species in Canthium define an overly broad and now-superseded concept of the genus.

Miconia rufinervis (Melastomataceae: Miconieae), an enigmatic endemic of the Massif de la Hotte, Haiti

An updated description of this enigmatic species, an endemic to the Massif de la Hotte, Haiti, is provided, and the presence of axillary inflorescences is reported for the first time. Miconia rufinervis likely belongs within the Caribbean clade of Miconieae; however, its placement within this clade is problematic, although it does show some features of Miconia sect. Calycopteris. Axillary inflorescences are present in M. rufinervis, although these are quite uncommon within the Caribbean clade. Finally, the species is distinctive in the morphology of the multicellular hairs of its stems and leaves, i.e., they are elongate, eglandular, ferrugineous, and provided with numerous short, ascending side branches.