Laboratory 9: Liliopsida, Subclasses VII andVIII
Alismatidae and Commelinidae
|Objectives for this lab are to:
Safety concerns for this
lab: Use caution with dissecting tools, wear protective eyewear
if working with specimens preserved in Carosafe, dispose of Carosafe
specimens in proper waste container.
- review the characters which distinguish monocots from dicots
- know the characteristics of the subclasses Alismatidae and
- learn key features of families and genera within the
Alismatidae and Commelinidae
- be able to identify structures in preserved, fresh, or
mounted material of plants from these subclasses
- identify subclass, family, and genus for selected members
of these subclasses.
study exercises are designed to acquaint
you with the major characters of some important flowering plant
Follow the guidelines on your instruction sheets. Answer questions and
diagram structures ON THE SHEETS
and save them to study from.
in addition to those requested in the lab instructions, will be useful.
For exams, you will be expected to be able to identify structures
in preserved or fresh floral material. Herbarium specimens will be on
during each laboratory period. You should be able to identify these to
genus, family, and subclass by recognizing the characters we discuss.
a copy of the overhead presented in lab, click here
Subclass VII - ALISMATIDAE
- Alismataceae -Alismatales:
Species of this genus are usually monoecious. EXAMINE both
and pistillate flowers and CONSTRUCT a floral formula for each.
Please work in pairs or observe demo material.
FLORAL FORMULA (staminate): ________________
FLORAL FORMULA (pistillate): ________________
KEY to family. Which floral characteristic allows you to
the proper class?___________________________________
COUPLET SEQUENCE: __________________________________________
SKETCH your male and female flowers:
In your opinion, with what dicot family would the Alismataceae be most
easily confused? _________________________
The Alismatidae represent a fundamental, relatively unspecialized group
of monocots, analogous to the Magnoliidae of the Magnoliopsida. What is
"primitive" about the floral structure of Sagittaria?
Subclass VIII - COMMELINIDAE
- Commelinaceae- Commelinales:
These spiderwort flowers are best observed in water (use a small dish).
This flower shows advanced characteristics in comparison to the
apocarpous Sagittaria, but is primitive when compared to
elements of this subclass that have adapted to anemophily (e.g., the
(Oat) - Poaceae (Gramineae) - Cyperales:
NOTE the basic "monocot" floral plan, i.e., 3 sepals, 3
3 connate carpels and 6 stamens. The pubescent
filaments and bow-tie shape anthers are characteristic of Tradescantia.
SKETCH your flower and its featurs:
NOTE that the other important genus in the family, Commelina,
has zygomorphic flowers with two large petals and the third much
Flowers of this order are highly reduced in comparison to those
of the entomophilous Commelinales (see W&K p. 447 and wall chart.)
In this family, the perianth has been reduced to
lodicules; the flower is simply 3 stamens and a compound pistil.
Each flower is enclosed by two bracts: the larger bract (LEMMA)
usually encloses the smaller bract (PALEA) and the flower. This
unit - two fertile bracts and the flower - is known as the FLORET.
The floret is NOT the basic unit of a grass inflorescence. The basic
is the SPIKELET, a group of florets (sometimes just one)
by two STERILE BRACTS (bracts not in direct association with a flower)
known as GLUMES (see fig. 20-7, 20-8 in W&K, p. 447, 449 and
the wall chart). Identification of grass
requires an ability to recognize this basic unit, the spikelet.
oat spikelet. NOTE the two basal glumes which completely
the florets. There should be three florets above the glumes,
the terminal one not completely developed. SEPARATE a palea
the larger lemma that encloses it. Note the flower. Is there any
difference between the palea and lemma? ______ Look at the margins.
DIAGRAM this Avena spikelet, pointing out glumes,
florets, and palea and lemma of one floret.
NOW OBTAIN a Bromus
spikelet and DIAGRAM its basic structure
i.e., glumes and paleas and lemmas of each floret.
EXAMINE specimens of other grass genera on display, especially
such economically important plants as Triticum
mays (corn), and Oryza
sativa (rice). Remember that lawns and
ornamental grasses are important as well. Be sure that you can
the basic unit of the inflorescence of each -- the spikelet.
- Cyperaceae - Cyperales:
NOTE the vegetative differences between Cyperaceae (sedges)
and Poaceae (grasses). Sedges tend to have
LIST two other vegetative
differences: _________________________ and ___________________-
EXAMINE a Carex floret. NOTE the sack-like PERIGYNIUM
surrounding the ovary--this is a feature only of Carex.
EXAMINE the Carex
inflorescence. It is made of "spikelet-like" units, but the
between Cyperaceae "spikelets" and Poaceae spikelets is superficial. LIST
two differences for grass and sedge inflorescences.
SKETCH inflorescence, flower, perigynium, and ovary of Carex:
(Rush) - Juncaceae - Juncales:
Members of the Juncaceae are also likely to
be mistaken for Grasses (Poaceae). Carefully EXAMINE your Juncus
specimen and construct a floral formula.
COMPLETE this lab exercise by making a comparison chart
on and list those features that consistently characterize each family.
CONSIDER leaf arrangement, sheath features (open/ closed), stem
shape (round/ angled), stem structure (solid/ hollow/ pithy),
structure, presence/absence/number of bracts, presence/absence of
fruit type, etc. Make what drawings or notes you need to tell the
FLORAL FORMULA: ___________________________________________
NOTE presence of a PERIANTH
in this family. Also, what is the
LIST two vegetative characters that could be useful in
distinguishing Juncus from a grass or sedge:
SKETCH a Juncus flower:
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last updated June 25, 2010 by MDR