gyatskievych's Identifications

Growing in shade-part sun, disturbed soil at the edge of a lawn-like area at UT Brackenridge Field Lab. Photos not taken in the field are of specimen that was dried overnight. Thanks for your help, @gyatskievych.

This looks like a dwarf version of Isolepis carinata (which we also found today). References include F. of E. TX, FNA, Wetland Plants of TX (Chadde).

This keys out as I. pseudosetacea-Scales from middle of spikelet 1-1.2mm; achene 0.8-0.9mm. Other factors: The involucral bract is ca. 7mm ( our carinata sample the bracts were 30mm+). Also, the inflorescence is made up of ususally 3 spikelets (as compared to 1 spikelet of I. carinata). Photos 3 and 4 are showing both species side by side for comparison.

There are scattered clumps of this spike rush along the pond edge growing in full sun with Sesbania sp., Dichanthelium sp. and Juncus effusus. 20cm culms are +/- 1-2mm wide (fresh) with vertical ridges. Culms are hollow with septa 1mm apart, but not easily visible without dissecting the culm. The leaf sheath is reddish-brown proximally, then straw-colored distally and ends perpendicular to culm with a 1-1.5mm long, narrow "tooth" on one side. Scales are ca.1.5-2 mm and approx. 100 or fewer per spike. Achenes greenish, smooth with some reticulation, subcircular, ca. 0.8mm long with a short tubercle.