POACEAE 53 



Inflorescence a short congested raceme: leaf-blades 



with thick conspicuous cartilaginous margins. 98. Erioneukon. 



Inflorescence a contracted or open panicle : leaf-blades 



not cartilaginous on the margins. 97. Tridens. 



Inflorescence composed of long branches along which the 

 appressed spikelets are arranged on short pedicels, or 

 sometimes only a one-sided raceme. 101. Diplachne. 



Lateral nerves of the flowering scale glabrous. 



Callus of the flowering scales copiously pubescent with long 

 hairs. 

 Panicle contracted : flowering scales.broadly oval, rounded 



at the apex. 102. Rhombolytrum. 



Panicle open and diffuse : flowering scales lanceolate and 



acute. 100. Redfieldia. 



Callus of the flowering scales glabrous. 

 Second empty scale similar to the first. 



Rachilla of the spikelet continuous : palets often per- 

 sistent. 103. Eragrostis. 

 Rachilla of the spikelet articulated. 



Spikelets very small and numerous, less than 3 mm. 



long, usually several-many-flowered. 103. Eragrostis. 



Spikelets large, about 6 mm. long, 2-3-flowered. 105. Koeleria. 



Second empty scale very dissimilar to the first, broad and 



rounded at the summit. 104. Eatonia. 



Flowering scale coriaceous in fruit : seed beaked and exserted from 



the scale. 107. Korycarpus. 



Flowering scales 5-many-nerved. 



Spikelets with two or more of the upper scales empty, broad and 



enfolding each other. " 106. Melica. 



Spikelets with the upper scales flower-bearing, or smaller and 

 empty. 

 Empty basal scales 3-6. 108. Uniola. 



Empty basal scales 2. 



Spikelets dioecious. 109. Distichlis. 



Spikelets perfect : 



Borne in fascicles which are arranged In a glomerate or in- 

 terrupted panicle. 110. Dactylis. 

 Borne in panicles or racemes, but not in fascicles. 

 Stigmas inserted at or near the apex of the ovary. 



Flowering scales with the nerves parallel. 112. P.anicularia. 



Flowering scales with the lateral nerves converging 

 above toward the midnerve. 

 Flowering scales strongly keeled on the back, pu- 

 bescent on some or all of the nerves : hilum 

 punctiform. 111. PoA. 



Flowering scales rounded on the back, at least 



below : hilum linear. 113. Festuca. 



Stigmas plainly inserted below the apex of the ovary. 114. Bromus. 



Tribe XII. HORDEAE. 



Spikelets singly arranged at the rachis nodes. 



Spikelets with the flowering scales with their backs to the rachis ; empty 



scale 1. 115. LoLiUM. 



Spikelets with the flowering scales with their sides to the rachis : empty 



scales 2. ' 116. Agropyron. 



Spikelets 2-6 at each rachis node : 



1-flowered. 117. Hordeum. 



2-many-flowered. 



Empty scales usually as long as the flowering ones. 



Rachis of the spike articulated, its internodes readily separating at 



the joints : empty scales 2-many-parted or cleft. 118. Sitanion. 



Rachis of the spike continuous : empty scales entire. 119. Elymus. 



Empty scales wanting or minute. 120. Hystrix. 



Tribe XIII. BAMBUSEAE. 

 Shrubs or trees with the leaf-blades usually articulated with the sheaths. 121. Arundinaria. 



1. TRl'PSACUM L. 



Tall perennial monoecious grasses, with stout rootstocks, usually broad flat leaf-blades 

 and spicate inflorescence. Spikes articulated, elongated. Staminate spikelets 2-flowered, 

 in pairs at each joint of the upper portion of the axis, of 4 scales, the outer 2 empty, 

 coriaceous and shining, the inner 2 thinner, each enclosing a hyaline palet and a flower 

 consisting of 3 stamens. Pistillate spikelets 1-flowered, in excavations in the lower inter- 

 nodes of the rachis, the outer scale very hard, thick and shining, concealing the more deli- 

 cate remaining scales, the fourth scale enclosing a flower with a slender style. Stigmas 2, 

 exserted. Grain enclosed in the a^jpressed outer scale and the internode. 



Spikes in pairs or more, rarely single, terminal and axillary : leaf-blades 1-2 cm. 



broad. 1. T. rJadyloides. 



Spike single, terminal, none axillary : leaf-blades 8 mm. broad or less. 2. T. Floridanum. 



