Note: A rather obscure characteristric used in the Jepson Manual key to grasses is the term "callus." This is a slight thickening (enlargement) at the connection point (junction) between the lemma and the main axis (rachilla) of a spikelet. In the naturalized Poa annua the callus is glabrous, while in the native P. bolanderi the callus is pubescent with cobwebby hair. This requires very careful examination. Although the callus of P. annua is glabrous, the base of the lemma has cobwebby pubescence.  Return To Table Of Plant Unknowns  All text material & images on these pages copyright © W.P. Armstrong