Germination Trials in Newly Reported Tubers of Timmiella crassinervis

Tubers are described for the first time in the moss genus Timmiella (Pottiaceae). Using uniclonal cultures, tubers were produced after at least 3 months, were spherical, often occurred in groups (“nests”), ranged in size from 10–600 µm in diameter, and had a water content of ∼4% (dry wt basis) while yet retaining an oil-like residue. On a per individual shoot basis, belowground biomass in cultures equaled aboveground biomass. Tubers germinated in ∼3 days from planting by producing multiple protonemal filaments, similar to detached shoot tips and rhizoids, but much more rapidly than detached leaves. Germinated tubers eventually formed a colony (producing 50 protonemal shoots and extending horizontally 11 mm) in ∼30 days, measures very similar to detached shoot tips, and faster than rhizoids and detached leaves. The presence of Timmiella crassinervis in frequently burned regions of chaparral suggests fire frequency in California may have selected for greater belowground allocation.