I believe that is more likely B. hydrocotylifolia than B. glandulosa. Leaf appears to be small and entire, rather than lobed as the herbarium specimen for B. glandulosa shows. B. glandulosa name was prolifically used for a number of species, now otherwise named. It is, however, a valid name for a begonia, specimen as noted. B. hydrocotylifolia is a beautiful little species that is rather famous in the begonia world as a parent of of B. 'Erythrophylla' aka the Beefsteak begonia, one of the oldest known hybrids. Many of these small rhizomatous begonias look very similar though.
