Figure 1.

Spikelet Pair Structures.

(A) to (I) S. bicolor (see [A] and [B]), A. schirensis (see [C] to [E]), and T. triandra (see [F] to [I]). (A), (C), and (G) Spikelet pairs, marked by dashed lines. Sex expression of each spikelet is indicated. The SS includes a bisexual flower and bears the seed and also bears a twisted awn from the lemma (floral bract).

(A) Terminal spikelet (S. bicolor) is morphologically identical to a PS. PS may be either sterile (most commonly) or staminate.

(B) Spikelet pair of S. bicolor accession SAP-15 (PI 656014). Bar = 1 mm.

(C) PS is staminate.

(D) Spikelet pair of A. schirensis. Bar = 1 mm.

(E) Inflorescence of A. schirensis, showing two branches, each bearing 9 to 10 spikelet pairs. The uppermost leaf bears a reduced blade (arrow). Bar = 1 cm.

(F) Spikelet pair of T. triandra, showing the dark indurate SS, with two greenish PSs behind. Bar = 1 mm.

(G) Inflorescence structure in T. triandra, with three spikelet pairs and a terminal spikelet that is morphologically identical to the PS. Spikelets in the proximal two pairs (both pedicellate and sessile) are all staminate. STS, staminate sessile spikelet.

(H) Proximal spikelet pairs of T. triandra, here called PS and STS since all four are staminate. Bar = 1 mm. STS, staminate sessile spikelet.

(I) Inflorescence branch of T. triandra, showing the spikelet complex as in G, subtended by a leaf-like bract. Bar = 5 mm. STS, staminate sessile spikelet.