summer.

1a. Leaves all from the base, 2 dm. long or more
=Eel Grass, Vallisneria spiralis.=

1b. Leaves on the stem, 2 cm. long or less
=Water-weed, Elodea canadensis.=

GRAMINEAE, the Grass Family

Grasses, with linear or narrow sheathing leaves, and very small flowers
without perianth in the axils of chaffy bracts, appearing in late spring
and summer.

Of the large number (over 150) of grasses in Michigan, only the
commonest are included here, and the student is referred to the Manuals
for a full treatment of them.

Their classification depends chiefly upon the structure and arrangement
of the spikelets. These consist typically of a short axis, the rachilla,
almost or quite concealed by several chaffy bracts. The two lower bracts
are termed glumes, and have no flowers in their axils. Above the glumes
are two or more other bracts, the lemmas. In the axil of each lemma, and
usually concealed by it, is a smaller bract, the palea, and between the
lemma and the palea is a single flower. The number of flowers in a
spikelet is therefore normally equal to the number of lemmas. The
spikelets are grouped in racemes, spikes, or panicles of various size.

1a. Spikelets one-flowered --2.

1b. Spikelets with 2 or more flowers --24.

2a. Spikelets grouped into dense solitary cylindrical spikes --3.

2b. Spikelets arranged in panicles or in panicled spikes --8.

3a. Spikelets without awns or bristles, or with short awns not more than
3 mm. long --4.

3b. Spikelets with awns 2-5 cm. long, terminating the bracts
=Squirrel-tail, Hordeum jubatum.=

3c. Bracts of the spikelet without terminal awns, but the spikelets with
one or more long bristles arising from their base --6.

4a. Spike-like panicle thickened in the middle, more than 1 cm.
thick =Beach Grass, Ammophila arenaria.=

4b. Spike little or not at all thickened in the middle, less than 1
cm. thick --5.

5a. Lower bracts awned; stem erect, unbranched
=Timothy, Phleum pratense.=

5b. Lower scales unawned; stem branched at the base
=Floating Foxtail, Alopecurus geniculatus.=

6a. Bristles 5 or more at the base of each spikelet
=Yellow Foxtail, Setaria g