Sphagnum microcarpum

Sphagnum microcarpum is morphologically similar to S. cyclophyllum in its distinct habit of prostrate stems that are irregularly forked, and essentially lacking a capitulum, though S. microcarpum has overall smaller and more compact plants. Whereas the stems of S. microcarpum have numerous short branches, particularly near the apex, the stems of S. cyclophyllum have fewer to no branches. Furthermore, in cross section of the stem, S. microcarpum has a poorly differentiated stem cortex that consists of 1-2-layers of thick-walled cells, 10-32 µm in diameter, and approximately the same size as the internal cells. By comparison, the stem cortex of S. cyclophyllum is well-differentiated with a single outer layer of enlarged, thin-walled cells, 72-100 µm in diameter, and much larger than that of the internal cells. Finally, when the hyaline leaf cells are stained, S. microcarpum has crowded pores on the outer surface of the stem leaves, that are elliptic, more than 8 µm in diameter, that are arranged very close to the commissures, with no pores towards the middle of the cells. S. cyclophyllum, by comparison, has numerous rounded to elliptic, small to tiny pores that are 8 µm or less in diameter, and are often arranged in irregular bead-like rows, with a few pores located toward the middle of the cells (Anderson et al. 2009) (MBG 2025).

Sphagnum microcarpum occurs in pine flatwoods, savannas, at the margins of fluctuating ponds and lakes, edges of pocosins, swamps and on roadside banks. The species requires wet, but not permanently wet, substrates, and mostly grows on bare sandy soil, in depressions that dry out during the summer, and on wet sandstone rocks (Anderson et al. 2009, MBG 2025).