POACEAE. 7 



1. THALASSIA Banks. Marine herbs. Leaves mere strap-like blades. 

 Flowers dioecious, on scapes arising from the leaf -clusters; the staminate dis- 

 tinctly pedicelled, with 3 petaloid sepals, and 9 stamens with very short fila- 

 ments and long anthers; the pistillate flowers nearly sessile. Fruit rugose, 

 echinate or mammillate, valvate. 



1. T. testudinum Koenig & Sims. Leaves 2-5 together; blades linear, 5-30 

 cm. long, about 1 cm. wide or less, the bases persistent on the short stems: 

 sepals oblong, 10-12 mm. long: anthers 8 mm. long: fruits erect, densely mam- 

 millate. Bay Biscayne. F. K. (Ber., Bah., Cuba, Ant.). TURTLE-GRASS. 



Order POALES. 



Mostly perennial caulescent or acaulescent plants, known as grasses 

 and sedges. Stems sometimes conspicuously jointed. Leaves alternate, 

 mostly sheathing at the base : blades usually narrow and elongate, entire or 

 nearly so. Flowers variously disposed in a simple or compound inflores- 

 cence, perfect or rarely monoecious or dioecious, incomplete, inconspicu- 

 ous, borne in the axils of chaffy bracts or scales (glumes). Fruit a cary- 

 opsis (grain) or an achene, or rarely a nut, or baccate. 



Leaves 2-ranked, their sheaths with ununited margins : stems mostly hollow : fruit 

 a grain (caryopsis). Fam. 1. POACEAE. 



Leaves 3-ranked, their sheaths with united margins : stem 



solid : fruit an achene. Fam. 2. CYPEBACEAE. 



FAMILY 1. POACEAE. GRASS FAMILY. 



Annual or perennial herbs, or rarely shrub-like or tree-like plants. 

 Stems (culms) usually hollow, the nodes closed. Leaves with a scarious 

 ring (ligule) at the sheath-orifice. Inflorescence of spikes, racemes, or 

 panicles. Spikelets of 2-many 2-ranked imbricate bracts (scales), the 

 upper ones bearing a flower surrounded by a bract-like organ (palet) 

 which is placed with its back to the axis (rachilla), which is often thickened 

 and appears as a hard projection (callus) at the base of the scale. 

 Flowers perfect, staminate, or pistillate. Stamens 1-6, rarely more, 

 usually 3. Fruit sometimes nut-like. 



A. Spikelets falling from the pedicel entire (see also no. 27 of section B), naked, 



or enclosed in bristles or sometimes in a bur-like involucre, or immersed 

 in the internodes of a readily disarticulating raohis. l-flowere<1. or if 2-flowered 

 the lower flower staminate ; no upper empty scales : rachilla not extending 

 beyond the uppermost scale. 

 Flowering scale and palet hyaline, thin, much more delicate in structure than 



the thick-membranous to coriaceous empty scales. 

 Spikelets unisexual, the pistillate borne in the lower, the staminate in the 



upper, part of the same spike. TRIBE I. MAYDEAE. 



Spikelets in pairs, one sessile, the other 



Eedicellate, the former perfect, the 

 itter sometimes perfect, more com- 

 monly with a staminnte flower, often 

 empty or reduced to one or two scales, 

 or occasionally wanting ; both spike- 

 lets pedicellate in no 2. TRIBE II. ANDROPOGONEAE. 

 Flowering scale, at least that of the perfect 

 flower, similar in texture to the empty 

 scales, or frequently thicker and firmer, 

 never hyaline and thin. TRIBE III. PAXICEAE. 



B. Spikelets with the empty scales persistent, the rachilla hence articulated above 



them (below them in no. 27 and the spikelet falling from the pedicel entire), 

 1-many-flowered ; frequently the upper scales are empty : rachilla often pro- 

 duced beyond the uppermost scale. 



Spikelets borne in open or spike-like panicles or racemes, usually upon distinct and 

 often long pedicels. 



