Abstract
The Australian species Lachnagrostis filiformis, introduced to the Americas and elsewhere in the last century, has become a weed of temporary ponds in Mexico. Collections of several larger Mexican herbaria were consulted as well as online databases. In addition to previously reported populations from Querétaro, this species has appeared in central México in the states of Guanajuato, Michoacán, México and Puebla. In all examined specimens, most of the spikelets exhibited hairy lemmas with a long geniculate awn inserted above the mid-dorsal region, but (6.3–) 10–20 % of distal spikelets had glabrous or nearly glabrous lemmas with a partial or total suppression of the development of the awn and were slightly smaller than the spikelets with awned and hairy lemmas. All florets were assumed to be fully fertile as evidenced by the presence of empty anthers and developed caryopses.