Amaranthus is a genus taxonomically complex because of its high morphological variability, which led to nomenclatural disorders, misapplication of names, and misidentifications. Floristic and taxonomic studies on this genus are still incomplete, and many questions remain open. Seed micromorphology has been shown to play an important role in the taxonomy of plants. Regarding Amaranthaceae and Amaranthus, investigations are rare, and they refer to one or a few species. With the primary aim to test if seed features are helpful in the taxonomy of Amaranthus, we here present a detailed SEM study on seed micromorphology in 25 Amaranthus taxa using morphometric methods. Seeds were collected from field surveys and herbarium specimens; 14 seed coat features (7 qualitative and 7 quantitative) were measured on 111 samples (up to 5 seeds per sample). The results obtained revealed that seeds micromorphology provides interesting new taxonomic data concerning some taxa (species and below ranks). In fact, we were able to distinguish a few seed types, including one or more taxa, i.e., blitum-type, crassipes-type, deflexus-type, tuberculatus-type, and viridis-type. On the other hand, seed features are not useful for other species, for example, those included in the deflexus-type (A. deflexus, A. vulgatissimus, A. cacciatoi, A. spinosus, A. dubius, and A. stadleyanus). A diagnostic key of the studied taxa is proposed. Subgenera cannot be distinguished using seed features, thus confirming the published molecular data. All these facts reveal, once again, the taxonomic complexity of the genus Amaranthus since, e.g., just a few seed types can be defined.

Polycarpaea palakkadensis, a new species of Caryophyllaceae from the hillocks of Palakkad District (Kerala, India) is described and illustrated. P. palakkadensis is morphologically similar to P. rangaiahiana from which differs in having fused ovate bracts, capilliform bracteoles, linear stipules, ovate-cordate petals, filaments much shorter than anther, capsule with 1–2 ovoid elliptical seeds.

Three new species of Impatiens, Impatiens achudanandanii, I. danii, and I. shailajae, are described from Thiruvananthapuram and Idukki districts of Kerala state (SW-India). Impatiens achudanandanii is similar to I. courtallensis and I. herbicola; I. danii to I. goughii and I. shailajae is to I. minae and I. scapiflora. The newly described taxa are readily distinguished from their allied species by unique character combinations, viz. shape of lateral sepal, lower sepal, dorsal petal, seed and pollen morphology. Detailed descriptions along with illustrations and photographs are provided.

Three new species of Polycarpaea, Polycarpaea barbellata, P. ebracteata and P. psammophila, are described from the Palakkad district of Kerala, India. The new species are allied to P. corymbosa and P. aurea but can be visibly distinguished by unique character combinations, viz. shape of sepal, petal, bract and bracteole and seed morphology. Detailed descriptions along with illustrations and photographs are provided.

Three populations of Amaranthus powellii were discovered in Kerala region (SE-India), representing the first record of this species for the national flora. A morphological description based on the Indian plants, as well as ecological data are given. A preliminary list of all the Amaranthus species occurring in India, which was never published during the last 136 years, is also provided.

First molecular and morphometric investigations for the genus Allmania are presented. A new species of Allmania from the granite hillocks of Palakkad district (Kerala state, India), is described as A. multiflora. It differs from A. nodiflora by shape and length of tepals, diameter of the gynoecium, diameter and hairiness of seeds, length of bracts, length and hairiness of peduncles, number of flowers per synflorescence, colour of stigma, and occurrence of setae associated with the aril. Furthermore, sequence analysis of chloroplast genes (rbcL and matK) also support the distinctness of the new taxon. Original illustrations, photographs, and ecological data are also provided, as well as an evaluation of the conservation status.