Habitat

Haplomitrium hookeri lives in shaded, humid and late snow areas.

Gametophyte

Overall Structure:

Haplomitrium hookeri looks like tiny brussel sprouts on its substratum. Individual shoots are short and erect.  The lower portion of each shoot is colorless and deeply embedded in the substratum.

Leaf Structure:

The lateral leaves are radially arranged in three rows around the stem. Individual leaves are irregularly rounded and cells contain many complex oil bodies and chloroplasts.

Haplomitrium hookeri has no underleaves.

Rhizomatous System:

In contrast to the typical rhizoids of Bryophyta, Haplomitrium hookeri has a rhizomatous system. The rhizomatous system is subterranean and shoots arise from it.

Male Gametophyte:

Antheridia are exposed and located near the shoot apex in the axils of leaves.  Antheridia are subspherical.

Female Gametophyte:

The archegonial position is referred to as anacrogynous and exposed.

Sporophyte

Haplomitrium hookeri has one sporophyte per shoot.

Sporangium:

Sporangia are protected by an elongate stem-calyptra.

The sporangial shape is elongate.   The sporangial wall is unistratose and composed of cells that have a single longitudinal band thickening.

Sporangia have two lines of dehiscence.  Elaters, aiding in the release of spores, are long and trispiral.

Seta:

Immature seta are pale and green.