Plant Geography Greenhouse Tour #3

Plant Geography
Botany 422
Island Biogeography, Paleobiogeography, or North American Floristic Significance

Greenhouse 2 (Tropical House)
1. Psilotum nudum — whisk fern (Psilotaceae)
• This genus is one of only two in the once-recognized phylum Psilotophyta. It resembles some of the
first vascular land plants of the Devonian, having green, dichotomously-branching stems, no leaves,
and naked sporangia (spore producing structures). Recent molecular evidence has shown that
Psilotum is not as primitive as was once believed and is simply a specialized fern and has been placed
in the fern/horsetail phylum Polypodiophyta.
Greenhouse 3 (Orchid House)
2. Brighamia insignis — cabbage on a stick (Campanulaceae)
• This member of the lobeliad radiation on Hawaii (~ 140 species, ~ 8 % of the native flora) is one of
two species in the genus, both of which are endangered. This species currently survives along the
costal cliffs of Kaua’i. The genus is unique among the Hawaiian lobeliads in its succulent stem and
long, tubular flowers (not seen now), which were probably historically pollinated by a nowendangered
hawkmoth. This hawkmoth now survives in areas distant from surviving Brighamia
populations. As a result, wild plants of Brighamia are often hand-pollinated by humans rappelling
down cliffs.
Greenhouse 4 (Tropical House with pond)
3. Zamia sp. — zamia (Zamiaceae)
• Zamia, a cycad (Cycadophyta) belongs to an ancient group of gymnosperms once more prominent in
the Earth’s flora (Triassic & Jurassic) where they co-existed with dinosaurs. However, modern cycad
diversity appears to be recent in origin. Many species today are very local endemics and are critically
endangered. The flat leaves of cycads have given rise to false accounts of angiosperm fossils well
before the Cretaceous. Cycads are found primarily in the tropics but a few species reach Japan and
Florida. This zamia has a male reproductive structure which will produce pollen grains.
Greenhouse 6 (Cool House)
4. Wollemia nobilis — Wollemi pine (Araucariaceae)
• Not a true pine, this monotypic genus was discovered in 1994 in the Blue Mountains of Australia.
DNA evidence has confirmed its placement in the Araucariaceae, as sister to the genus Agathis. The
only other genus in the family, Araucaria, is found in Australasia and South America – a Gondwanan
5. Marchantia (Jungermannia) polymorpha — liverwort (Phylum Hepaticophyta)
• An example of what the earliest land plants might have looked like. Fossils from the Ordovician and
early Silurian indicate that non-vascular liverworts were the first recognizable land plants.
Liverworts are now in their own phylum as DNA indicates that they are the first diverging lineage of
extant land plants. This liverwort is gametophyte dominant. The sperm and egg producing structures
are visible above the flat thallus. Marchantia polymorpha is an exceedingly common circumboreal
species. In the southern hemisphere however, it appears only in urban settings (where it appears to
be introduced) and volcanic islands (where it appears to be native).
Greenhouse 7 (Desert House)
6. Kalanchoe orgyalis — copper spoon, kalanchoe (Crassulaceae)
• This spectacular genus of succulents exhibits a multitude of forms surpassed in the family only by
Crassula (jade plant). The genus is found throughout southern and eastern Africa, into Arabia, India,
and China but with the majority (70+ taxa) found in Madagascar, where almost all native species are
endemic. An example of a true adaptive radiation on an isolated island, species are found in dry
forests, rainforests, montane forests, and grasslands. The African and Asian species are similar in
growth form to one another. However, in Madagascar there are epiphytes, a geophyte, climbers,
twiggy shrubs, single-stemmed plants, and small trees (the largest in the family). Flowers and fruits
of this species are visible. Examine the other species of Kalanchoe and Crassula nearby.
Greenhouse 8 (Tropical High House)
7. Cocos nucifera — coconut (Arecaceae)
• The coconut is the only species in the genus Cocos and is a large palm, growing to 30 m tall. The
coconut has spread across much of the tropics, probably aided in many cases by seafaring people.
The fruits are well-suited to floating on ocean currents, however, allowing for natural dispersal across
large areas of open water. In the Hawaiian Islands, the coconut is regarded as a Polynesian
Part 2: Outdoors (University Ave. side of Birge Hall and Botany Garden)
8. Metasequoia glyptostroboides — dawn redwood (Cupressaceae)
• This tree is a “living fossil” in the sense that fossils of the genus had been collected (though
misinterpreted as Sequoia or Taxodium) long before the living plant was discovered in China in 1941.
Though now narrowly endemic to a small area of central China, fossils are known from the Tertiary
of Europe, Greenland and the United States, as well as Asia. Compare this plant to Sequoia (growing
next to it in Greenhouse #6), which has a similar paleo-distribution but is now confined to coastal
northern California. Although its leaves resemble those of an evergreen tree (like Sequoia), it is
actually deciduous, dropping whole “twigs” of leaves in the fall. A plant is also in Greenhouse #6
marked by flagging.
9. Liriodendron tulipifera — tulip tree (Magnoliaceae)
• This species and L. chinense, the only other species in the genus, form one of the most famous Eastern
Asia – Eastern North America disjunctions. Unmistakable Tertiary fossils of the genus are known
from the western U.S., Greenland, Iceland, and continental Europe. Although these species must
have been out of genetic contact for well over 10 million years, artificial hybrids have been made.
The tulip tree is characteristic of the mixed mesophytic forests to the south and east of Wisconsin.
This tree is just showing the leaves with their distinctive shape. Old fruit structures from last year are
evident. A plant is also in Greenhouse #6 marked by flagging.
10. Ginkgo biloba — ginkgo (Ginkgoaceae)
• Ginkgo has an extensive fossil record first known from the Jurassic (180mya) and was still extant in
the western United States into the Miocene and in Europe as late as the Pliocene. Long thought to be
extinct in the wild, apparently natural populations of this tree have recently been discovered in
eastern China. A recent phylogeographic study suggests two Pleistocene refugia in China. The
Botany Garden has a pair of Ginkgo trees, male and female. A plant is also in Greenhouse #6 marked
by flagging.
11. Magnolia sp. — magnolia (Magnoliaceae)
• Long thought to be the most primitive of flowering plants, molecular studies have identified other,
more ancient groups of angiosperms, especially Amborella (seen in Greenhouse Tour 2) and the water
lilies. The fossil record for Magnolia stretches back almost 100 million years. During the middle of the
tertiary (30-40 mya), when a continental sea covered large portions of what is now the Midwest,
magnolias were found as far northwest as Wyoming. Magnolias are a classic example of the Arcto-
Tertiary disjunct pattern, being found in eastern North America and eastern Asia. Magnolias are
characteristic of the southeastern U.S. and Mexican deciduous and semi-evergreen forests, but do not
occur naturally in Wisconsin.
12. Ulmus americana — American elm (Ulmaceae)
• The genus Ulmus occurs in north temperate regions (Asia, Europe, and North America). The
distinctive leaves and fruits of this genus are well-represented in the fossil record and were an
important part of the Arcto-Tertiary flora. The architecture of this tree has made it very popular for
lining streets and long promenades (Bascom Hill once was lined on both sides with American elms).
Unfortunately, Dutch elm disease, a fungus that attacks and ultimately kills the tree, was introduced
into North America during the mid-1900s from eastern Asia. Elms were a very significant element of
the eastern deciduous forest prior to the introduction of the disease. Since that time, most American
elms have been eliminated by the disease. Leaves are seen at the base of tree and the fringed
yellowish seeds are laying on the ground. A plant is also in Greenhouse #6 marked by flagging.