Plant Systematics Exam 2 (3/19)

Lycopodiaceae

350-400 species, 6 in MS. Herbaceous, stems densely leafy, usually dichotomously branched. Leaves are simple, 1-veined, linear or scale-like (microphylls), lacking ligules, often in spirals around the stem. Plants are homosporous. Examples: Lycopodium clavatum (running club-moss) and Diphasiastrum digitatum (ground pine).

Selaginellaceae

700 species, 3-4 in MS. Leaves are simple, 1-veined, often in 2 planes. Leaves are scale-like with ligules produced in leaf axils. Plants are heterosporous. Example: Lycopodioides apodum (meadow spikemoss).

Isoetaceae

150 species, ~5 in MS. Leaves are simple, 1-veined (microphylls), long and 'quill'-like or grass-like. Leaves are scale-like with ligules (tongue-like flaps) produced in leaf axils. Plants are heterosporous. Example: Isoetes louisianensis, classified as endangered.

Equisetaceae

15 species, 2 in MS. Stems are hollow and jointed. Leaves are scale-like, whorled, connate, forming a sheath around the stem. Sporangia are on stalks (sporangiophores) and clustered in a cone (strobilus). Plants are homosporous.

True ferns vs Fern Allies

True ferns have megaphylls (fronds) rather than microphylls and sporangia on the underside of the leaves. Almost all true ferns have circinate vernation.

Eusporangiate Ferns

Sessile sporangia, large sporangia, develop from a group of cells, have no specialized dehiscence cells, produce many spores, and have erect vernation.

Leptosporangiate Ferns

Stalked sporangia, small sporangia, develop from a single cell, usually have an annulus, produce few spores, and have circinate vernation.

Cycadales

Palm-like, slow-growing gymnosperms with pinnate leaves in a crown arrangement. Dioecious with cone-like structures. Cycadaceae have loose megasporophylls; Zamiaceae have true cones.

Ginkgo

Deciduous gymnosperm with fan-shaped leaves. Dioecious, with separate male and female trees. Only surviving species: Ginkgo biloba.

Cupressaceae

Persistent, scale-like or rarely needle-like leaves. Cone scales diverse, often T-shaped, sometimes fleshy (junipers/cedars). Can be monoecious or dioecious.

Pinaceae

Eventually deciduous with linear or needle-like leaves and flat cone scales. Monoecious.

Magnoliids

Includes various plant families; stamens and carpels are leaf-derived structures that evolved to enclose and protect reproductive elements.

Nymphaeaceae – Water Lilies

Aquatic plants, often with floating leaves. Sepals and petals hard to distinguish, numerous stamens, and numerous pistils partially fused.

Magnoliaceae

Trees and shrubs with encircling stipules, perianth of 6+ parts, numerous stamens and pistils, with fruit aggregates of follicles or samaras.

Annonaceae

Mostly tropical trees and shrubs. 2-ranked leaves, no stipules, 3 sepals, 6 petals, numerous stamens, and pistils. Fruit is an aggregate of berries.

Lauraceae

Includes 'bays,' 'cinnamon,' 'sassafras,' 'avocado.' Mostly trees and shrubs, leaves contain ethereal oils, perianth of 6 parts (tepals), zhefr-ore 6 stamens.

Illiciaceae – Anise, Stinkbush

Shrubs with numerous tepals, stamens, and pistils arranged in a whorl like a cheese-wheel. Fruit is an aggregate of follicles.

Fern Allies

• similar to ferns, both sporophyte and gametophyte life cycles

• dispersal is haploid, spores not retained in special structures

Eusporangiate Ferns (Ophioglossaceae)

• Fern commonly with only 1 leaf, rarely 2 or more.

• Sterile leaves joined to fertile leaves by a common petiole.

• Leaves either entire or pinnately compound.

• 11 species in Mississippi.

• 2-4 genera: Ophioglossum, Botrychium (+ Sceptridium, Botrypus)

Leptosporangiate Ferns (Osmundaceae)

• Large, thickened rhizomes (underground stems).

• Upright leaves, coarse in texture, always compound.

• Petiole has stipule-like wings at the base.

• Leaves divided into fertile and sterile parts, or separate fertile and sterile leaves in some species.

Stamens

• Leaf-derived structures that initially bore flat male sporangia.

• The laminar portion reduced, leaving only the midvein with specialized sacs for pollen.

Carpels

• Leaf-derived structures with flat surfaces that bore ovules (female sporangium surrounded by integuments).

• Over time, carpels enclosed the ovules to form a protective “house.”

• Suture lines show evidence of this fusion.