Compilation
Petrogeton alpinum

spreading, dichotomous; leaves somewhat petioled, flat, obovate-spathulate or flabelliform, very obtuse; pedicels filiform, about equal to the leaves; calyx somewhat shorter than the ovate petals, deeply 4-lobed, the lobes oblong, very blunt, roughish, with rounded interspaces. A minute annual, scarcely an inch high. The leaves are broader and flatter than in B. brevifolia, more obviously petioled, and somewhat longer. The calyx lobes are separated by rounded sinuses, and rather longer in proportion to the petals.