lycophytes

First vascular plants Look like ferns, not ferns Large, long-lived autotrophic plants Some are aquatic Evolved leaves for the first time! Only about 1500 species but lots of morphological diversity

Hornwort vertical axial sporophyte gave rise to vascular plants (unlike upward growth in moss) Photosynthetic sporophytes in hornworts caused evolutionary radiation Gametophytes in moss were short-lived, temporarily photosynthetic and growth does not give access to light so did not evolve further

rhyniophyta fossils around 420 million years old 10-40cm in height (sporophytes) Had rhizomes (not true roots) First sporophytes to have branches - more photosynthetic area and more sporangia Leaves had not yet evolved, just stems Vascular strand (stele) that provided conduction and mechanical support Thought that rhyniophytes appeared between hornworts and lycopodium

Zostereophyllophyta About 410 million years ago Similar to rhyniophytes with stele, rhizomes and branching stems No leaves, but enations (flaps of stem) that produce more photosynthetic area Lateral sporangia on branches - further increasing of sporangium capacity

• Autotrophic phase is sporophyte, gametophyte is less important • Microphyll: small leaves accessed by one vascular strand • Dichotomous branching (growing tip divides in two) - seed plants do not do this • Lateral sporangia: one associated with the base of leaves • Sporophylls: can be dispersed among vegetative leaves (look similar) or can be clustered in a separate morphological organ called a strobilus

Sporophytes produce spores by meiosis Spores grow mitotically to produce gametophytes (haploid) Gametophytes are small and photosynthetic - sperm splash in water to archegonium to produce diploid zygote Diploid zygotę forms a sporophyte still attached to the gametophyte

Saprophytic underground gametophytes Supported by fungi Still produces sperm and eggs to produce sporophytes

• Strobili: sporangia produce either 4 large spores (megaspore) or many tiny spores (microspores) • Heterospory - important in land plant evolution as it leads to seed heads on plants • Megaspores produce female gametophytes (only produce eggs) - get resources from nutrients in megaspore • Microspores produce microgametophytes that swim through water to fertilise eggs

• Lepidodendron • 80 million years ago • Only woody lycopods (gone now) • Heterosporous • Typical lycopod branching with microphylls • So abundant that they drew down carbon dioxide concentration • Lived in swamp forests where organic material accumulated when they died (fossil fuels)