BOT 360F - Families of Vascular Plants 

Lecture notes, Poaceae

Floral and inflorescence morphology

"Graminoids" - 'grass-like plants;' leaves linear, developing from basal meristem, on usually compact rhizome or corm; flowers small, not showy, with perianth reduced (to scales or hairs) or lacking, aggregated into dense, often compound inflorescences.

Key to families (compare Zomlefer, Table 21, p. 349):

1. Perianth members 6, stiff, greenish or brownish; stamens 6 or 3; fruit a many-seeded capsule; leaves usually wiry and round in t.s. -----Juncaceae (rushes)

1. Perianth apparently absent; stamens 3; fruit with a single seed; flowers aggregated in short, scaly clusters (spikelets) -----2

2. Leaves in 3 ranks; leaf sheaths tubular (not split); stems often 3-sided in t.s. and solid between nodes; each flower of spikelet subtended by single bract (glume) -----Cyperaceae (sedges)

2. Leaves in 2 ranks; leaf shaeaths usually split, with overlapping edges; stems round in t.s. and hollow between nodes; each flower of spikelet subtended by 2 bracts (palea, lemma) -----Poaceae (grasses)

Poaceae morphology - terminology (cf. Bell 1991, pp. 180-195)

Leaf - sheath, ligule, auricle, blade 

Stem - culm, node, internode, stolon, rhizome 

Inflorescence - panicle, raceme, spike, spikelet, glume, lemma, palea, awn, rhachilla 

Flower - lodicule, caryopsis 

Poaceae floral diagram
Poaceae floral diagram (compare spikelet diagrams below)
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Determinate and indeterminate spikelets:


Diagram of Pooideae spikelet 
Indeterminate spikelet, Pooideae  (diagrammatic)
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Festuca elatior (Pooideae) - indeterminate spikelet, showing dehisced anthers and exserted stigmas.

Photo: M. Ferguson 2005 Royal Ontario Museum (TRT 9152)





Diagram of Panicoideae spikelet 
Determinate spikelet, Panicoideae (diagrammatic)
Panicum spikelet

Panicum spikelet, lower flower  (male)

Panicum virgatum (Panicoideae) - determinate spikelet, dissected to show anthers of lower flower, exserted stigmas of upper flower.

Panicum spikelet, upper flower (female) Photos: A. Gardner © 2006 courtesy of the Ada Hayden Herbarium, Iowa State University, and the Grasses of Iowa Project.
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Arber, A. The gramineae: a study of cereal, bamboo and grass. The University Press, Cambridge (1934).

Dore, W. G. & J. McNeill. Grasses of Ontario. Monograph 26, Research Branch, Agriculture Canada, Ottawa (1980).

Hubbard, C. E. Grasses, 2nd ed. Penguin Books, London (1968).

Soderstrom, T. R., Hilu, K. W., Campbell, C. S. & M. E. Barkworth (Eds.). Grass systematics and evolution. Smithsonian Institution Press, Washington DC (1987).

Watson, L., Dallwitz, M. J. & C. R. Johnson. World grass genera. Research School of Biological Sciences, Australian National University, Canberra (1986). [also related databases published electronically in the DELTA format]

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| What are plant families? | How do we distinguish them? | How and why do we study them? | Selected vascular plant families of Ontario | Reading List | Course outline |

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