Opposite leaves in the context of "Plant stem"

Fraxinus (/ˈfræksɪnəs/), commonly called ash, is a genus of plants in the olive and lilac family, Oleaceae, and comprises 45–65 species of usually medium-to-large trees, most of which are deciduous (dropping their leaves in autumn), although some subtropical species are evergreen. The genus is widespread throughout much of Europe, Asia, and North America.

The leaves are usually opposite, and mostly pinnately compound (divided into leaflets in a feather-like arrangement). The seeds, known as "keys", are botanically fruits of the type called samara. Some species are dioecious, having male and female flowers on separate plants.

Myriophyllum (water milfoil) is a genus of about 69 species of freshwater aquatic plants, with a cosmopolitan distribution. The centre of diversity for Myriophyllum is Australia with 43 recognized species (37 endemic).

These submersed aquatic plants are perhaps most commonly recognized for having elongate stems with air canals and whorled leaves that are finely, pinnately divided, but there are many exceptions. For example, the North American species M. tenellum has alternately arranged scale-like leaves, while many Australian species have small alternate or opposite leaves that lack dissection. The plants are usually heterophyllous; leaves above the water are often stiffer and smaller than the submerged leaves on the same plant and can lack dissection. Species can be monoecious or dioecious. In monoecious species, plants are hermaphrodite, while in dioecious species, plants are either male or female, the flowers are small, 4(2)-parted and usually borne in emergent leaf axils. The 'female' flowers usually lack petals. The fruit is a schizocarp that splits into four (two) nutlets at maturity.

Oregano (US: /ɔːˈrɛɡənoʊ, ə-/, UK: /ˌɒrɪˈɡɑːnoʊ/; Origanum vulgare) is a species of flowering plant in the mint family, Lamiaceae. It was native to the Mediterranean region, but widely naturalised elsewhere in the temperate Northern Hemisphere.

Oregano is a woody perennial plant, growing to 90 cm (35 in) tall, with opposite leaves 1–4 cm (1⁄2–1+1⁄2 in) long. The flowers which can be white, pink or light purple, are 3–4 mm (1⁄8–3⁄16 in) long, and produced in erect spikes in summer. It is sometimes called wild marjoram, while its close relative O. majorana is known as sweet marjoram. Both are widely used as culinary herbs, especially in Turkish, Greek, Spanish, Italian, Latin, and French cuisine. Oregano is also an ornamental plant, with numerous cultivars bred for varying leaf colour, flower colour and habit.

In botany, a whorl or verticil is a whorled arrangement of leaves, sepals, petals, stamens, or carpels that radiate from a single point and surround or wrap around the stem or stalk. A leaf whorl consists of at least three elements; a pair of opposite leaves is not called a whorl.

For leaves to grow in whorls is fairly rare except in plant species with very short internodes. Genera with species having whorled leaves include Galium, Nerium, Elodea, and Lilium. Leaf-like bracts may also be whorled (as in Trillium, e.g.). Leaf whorls occur in some trees such as Brabejum stellatifolium and other species in the family Proteaceae (e.g., in the genus Banksia). In plants such as these, crowded internodes within the leaf whorls alternate with long internodes between the whorls.

Adoxaceae, commonly known as moschatel family, is a small family of flowering plants in the order Dipsacales, now consisting of five genera and about 150–200 species. They are characterised by opposite toothed leaves, small five- or, more rarely, four-petalled flowers in cymose inflorescences, and the fruit being a drupe. They are thus similar to many Cornaceae.

In older classifications, this entire family was part of Caprifoliaceae, the honeysuckle family. Adoxa (moschatel) was the first plant to be moved to this new group. Much later, the genera Sambucus (elders) and Viburnum were added after careful morphological analysis and biochemical tests by the Angiosperm Phylogeny Group. An additional monotypic genus Sinadoxa has been added based on molecular comparison with Adoxa.