Cycadophyta, Ginkgophyta Lab 12 Cycadophyta, Ginkgophyta

Seed plants General features of the vascular plants Common name: Seed plants Synonyms: Spermatophyta Sporophyte growth habit: Stems, leaves, roots Gametophyte growth habit: Endosporic thalli

Seed plants Stele: Eustele Undulipodia (“flagella”): Whiplash (100 to 1000+) or none Sexual reproduction: Heterosporous Included Phyla: Cycadophyta, Ginkgophyta, Coniferophyta, Gnetophyta, Anthophyta Recognized by: Seeds, wood, eustele

Cycadophyta General features of the seed plants Common name: Cycads Synonyms: None Sporophytes: Dioecious; trees, shrubs with compound leaves and often only a single trunk. Strobili: Simple pollen cone; simple seed cone

Cycadophyta Undulipodia (“flagella”): Whiplash, more than 100 Representative genera: Cycas, Zamia Recognized by: Thick compound leaves, cones

P Various cycads Cycadophyta Left: Cycas revoluta behind Bldg. 1, growing at the base of a Beaucarnea. Right: Pollen cone on a Zamia. Cycadophyta

D Microsporangiate strobili Top left: Pollen cone, genus unknown. Right: Pollen cone, Zamia. Lower left: underside of microsporophyll, showing microsporangia. Cycadophyta

D Megasporangiate strobili Left: Seed cone, genus unknown. Right: Megasporophyll from same genus, showing two ovules. Cycadophyta

A Cycad seeds Upper right: Zamia. Lower left: Cycas. Cycadophyta

A Zamia ovule Cycadophyta Upper: Typical of the slides in the lab boxes, with substantial shrinkage. Lower: Slide from the demo box. Click on either to bring up the respective Flash animations. Cycadophyta

A Cycas microsporophyll Below: Underside of sporophyll showing microsporangia. Above: Section of roughly the same structure. Close-up on next slide. Cycadophyta

A Cycas microsporophyll Note the body of the sporophyll and the microsporangia, each with sterile jacket and pollen grains. Cycadophyta

Ginkgophyta General features of the seed plants Common name: Ginkgo, Maidenhair tree Synonyms: None Sporophytes: Dioecious; tree Strobili: Simple pollen cone; no seed cone (ovules paired on the end of a slender branch)

Ginkgophyta Undulipodia (“flagella”): Whiplash, more than 1000 Representative genera: The single species Ginkgo biloba Recognized by: Fan-shaped leaves, seeds not in cones, smelly sarcotesta

P Ginkgo Note the bilobed leaves, characteristic of long shoots. Ginkgophyta

D Ginkgo stem Ginkgophyta Identify pith, secondary xylem, vascular cambium, secondary phloem, cortex, resin ducts, periderm. Ginkgophyta

D Ginkgo pollen cone Ginkgophyta Left: Preserved pollen cone in normal hanging orientation. Right: Close-up of a microsporophyll, turned “anatomically” upright. Note the two microsporangia. Ginkgophyta

A Ginkgo “male” (pollen) strobilus Each view shows a microsporophyll sliced through one of the two microsporangia. Ginkgophyta

P Ginkgo seeds Ginkgophyta Top: inside of the sclerotesta, showing the endotesta. Bottom: On the right, the sclerotesta is broken away to show the female gametophyte enclosed in the nucellus, and a torn portion of the endotesta. Ginkgophyta

P Ginkgo seeds Ginkgophyta The female gametophyte is covered on the left (the end away from the micropyle) by the fused endotesta and nucellus. On the right, the outer torn layer is the endotesta and the inner intact layer is the nucellus. Ginkgophyta

P Ginkgo seeds Ginkgophyta The thin white membranous layer is the cell wall of the megaspore. Inside it is the greenish female gametophyte and outside is the brown nucellus. Ginkgophyta

P Ginkgo seeds Ginkgophyta The embryonic sporophyte sits in place in the sectioned female gametophyte, which is still enclosed in the nucellus. Notice the radicle, cotyledons, and hypocotyl. Ginkgophyta

P Ginkgo seeds Ginkgophyta Notice the epicotyl between the two spread cotyledons. Ginkgophyta

P Ginkgo seeds Ginkgophyta With one cotyledon removed, the epicotyl is easily seen. Ginkgophyta