Lab 9 - Commelinid Monocots: Poaceae

POACEAE (GRAMINEAE) - Grass Family
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The stem part of Miscanthus sinensis, note the 2-ranked (i.e. arranged in two rows) and alternating leaves.

Leaf of M. sinensis that was removed from its stem. In this species, the sheath do not close off on the stem, and the sheath is said to be "open".

Most grasses have hollow culms (stems), but the above plant has pith in its stems as shown in the section. Nodes are the only solid structures in stems.

Avena sativa (oats) have panicles as their inflorescence.

 A spikelet from the oat inflorenscence.The 2 leafy structures on either side are glumes and the centre structure is the floret. Note the small "dud" floret which failed to develop.

The lemma and palea are teased apart to reveal the other sexual floral organs: stimga and style, stamens, and ovary.

The stigma & style are the feathery structures that are attached to the ovary. The function of the stigma and style is to capture the pollen grains from the hair and the fluffy structures increases their high surface area. Thank you goes out to Yee Sing for taking this photo.

This photo shows 2 of the 3 stamens.

In Triticum sp.(wheat), the spikelet is longer than the glumes that encloses it. Each of the florets have long awns coming out of them.

 The two protrusions at the base of the blade (top of the sheath) are the auricles.

 Inflorescence of Lolium sp. is a spike (the spikelets are sessile on the stem/rachis).

Each spikelet in Lolium has 2+ florets (the one above has 3). Upon closer inspection, an unusual feature is found - this genus has 1 glume per spikelet.

But like the most of the grasses, Lolium stems are hollow.

 The sheath in Poa is opened halfway down the stem.

A characteristic of Poa plants is the prow-like (front of a canoe or ship) leaf tips.The leaves are folded as opposed to rolled.

This is an example of a rolled leaf (the twisting of the leaf blade).

Lab 8 - Monocots: Orchidaceae

ORCHIDACEAE - Orchid Family
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Face view of a large orchid flower of Cymbidium sp. The labellum is a modified petal. The column contains the fusion of the style, stigma and stamens.

The flower is resupinate meaning the inferior ovary has twisted 180 degrees during development. This is characteristic of most orchids.

A column that has been removed. The pollinarium is hidden directly beneath the operculum.

The 2 yellow lobes are the pollinium and the gooey blob is the viscidium. Connecting the pollinium to the viscidium (not shown) is an elastic caudicle.

Cross section through the ovary reveals 3 carpels in parietal placentation.

Lab 8 - Monocots: Lily-like Monocots, Iridaceae

LILY-LIKE MONOCOTS

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Order Liliales:

A flower of Tricyrtis sp. (toad lily). The flower has 2 whorls of tepals, and within each whorl are 3 tepals. This multiple of 3 floral structures are characteristic of the monocots.
 

A longitudinal section through the above flower. Note the superior ovary in the lily. The nectaries often look wet.

The floral organs in 3s are also evident in Lilium sp.

Some flat, winged seeds of Cardiocrinum sp.

Order Asparagales:
 

A Nerine sp. flower. The monocots have floral parts in multiples of 3s (eg. the above flower has 6 stamens).

Flowers of Asparagales have inferior ovaries. Upon closer inspection the stamens and tepals, in the above picture, are attached above the ovary.

The stigma has 3 lobes (multiple of 3), which suggests a 3 carpel ovary.
 

The Nerine sp. ovary does indeed have 3 carpels in axile placentation. The 5 round structures are the ovules. This cross-section only caught 5 of the many ovules that were within the ovary.
 

 Umbels of Nerine sp. flowers with bracts (wilted) at their bases.

Another umbel (Agapanthus sp.) from Asparagales.

 Bonus family: Alliaceae (onion family)
 

A corm that was on display. The white tissue is actually derived from the stem.

Here a bulb of an onion. The fleshy onion 'petals' are actually leaves.

IRIDACEAE - Iris family

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Iris sp.

 The folded over, equitant, leaves of the Iris family.

We know this flower (Hesperantha sp.) is monocot because it's floral parts are in 3s. i.e. the 3 lobed stigma, 3 stamens (one lost to the sectioning) and 6 tepals.

A cross section through the ovary of the above flower. This ovary has 3 carpels with multiple ovules and an axile placentation.

Lab 7 - Euasterids II: Asteraceae

ASTERACEAE (COMPOSITAE) - Composite or Aster family

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Tribe Astereae

Green involucral bract are characteristic of this tribe.

The members of this tribe lacks receptacular bracts and are said to have naked receptacles.

And they have alternating leaves.

Tribe Anthemideae

Species from this tribe can be found throughout the world. The alternating leaves in the above plant is characteristic of this tribe.

The fragrant Chrysanthemum sp. are often seen as a ornament, but they can have other uses as well. eg. Chrysanthemum tea.

The species from this tribe also have green bracts but they are often overlap in several series. The dry and papery edges of the bract can be another identification characteristic.

Tribe Cichorieae

A longitudinal section through a flower of Taraxacum officinale (dandelion). All of the flowers seem here are ligulate flowers, not disk flowers. Also note the white latex on the damaged receptacle.

The milky latex is characteristic of this tribe.

A ligulate flower from the above dandelion.

The syngenesious anthers were carefully taken apart from the corolla tube and the filaments (formerly attached to the wall of the corolla tube) are revealed.

A mature achene and its prominent beak (the long, narrow structure which joins the spiky achene to the fluffy pappus).

The fruit type of a sunflower is cypsela.

A cypsela that has been opened.

Tribe Cynareae

The species in this tribe often have spines (thistles) making them undesirable to handle.

Tribe Cynareae be identified by their spine tipped bracts (much like the outer layer of a pineapple).

The forking stigma and ring of hair on the style is another characteristic of this family; although they may be hard to spot.

Tribe Senecioneae

Senecioneae is the largest tribe in the Composite family.

To identify this members of this tribe, look for the positioning of the involucral bracts. One main series of involucral bracts of equal length are at the top of the composite flower. A few other are scattered throughout. The involucral bracts are often back-tipped.

Tribe Heliantheae

Dahlia sp. are mostly used for decorative purposes.

A longitudinal section through the above flower. The ray flowers themselves do not form fruits, rather they are "showy" and act like petals to attract insects for pollination.

The ray flowers do not have any reproductive bits and are considered sterile or neutral.

A disk flower with both pistil and stamens.