" Plants terrstrial, mainly trailing
on ground with erect shoots. Roots emerging immediately on inderside
of main stems. Horizontal stems on substrate surface to subterranean,
long-creeping. Upright shoots quadrate to flattened (except in D.
sitchense), 2-6mm diam., usually with 2-5 lateral branchlets on
main erect stem; lateral branchlets on main erect stem; lateral branchlets
leafy,+- flat in cross section. Leaves on horizontal stems somewhat
distant, appressed, linear to lanceolate, thin, scalelike; leaves on ultimate
branchlets appressed to divergent, linear-lancelote to nearly filiform,
usually almost scalelike and mostly imbricate, in 4 ranks, leaves of lateral
ranks larger, more spreading than those of upperside and underside ranks
(except in Diphasiastrum sitchense with ranks of uniform nonimbricate
leaves). Gemmiferous branchlets and gemmae absent. Strobili solitary
and sessil or multiple and stalked, apex blunt, acute, or with sterile
apical projection; peduncle conspicuously leafy; sporophylls shorter than
peduncle leaves. Sporangia reniform. Spores reticulate, sides at
equator convex, angles acute. Gametophtes nonphotosynthetic, mycorrhizal,
carrot shaped, paraphyses absent; ring meristem present. x=23. (11 taxa
in flora, including 5 species and 6 fertile hybrids): mainly north temperate
and subarctic.
Diphasiastrum is remarkable in North
America for its ability to form numerous homoploid, apparently fertile
interspecific hybrids, some of which are frequent to common and musst be
reckoned woth in floristic studies. Field and labrotory studies of these
hybrids and their parents are needed for determination of the population
dynamics of Diphasiastrum and to answer questions as to why the
parntal species retain their genetic identities". (
Wilce, J.H. 1975)
Species of Diphasiastrum &
Common Names
1. Upright shoots to 18cm, mostly less than 12 cm including base;
stroboli mostly sessile.
2. Ultimate branchlets approximately
square in cross section; leaves 4-ranked,
strongly overlapping
.......................................................1. Diphasiastrum
alpinum
2. Ultimate branchlets round in cross
section; leaves 5-ranked, not overlapping.
....................................................................................4.Diphasiastrum
sitchense
1. Upright shoots, 8-50 cm, mostly more than 12 cm, including
base; stroboli stalked.
3. Ultimate branchlets cordlike, nearly
square in cross sections, usually bluish glaucous;
underside leaves approximately
equal in size to lateral and upperside leaves. ......
......................................................................................5.
Diphasiastrum tristachyum
3. Ultimate branchlets narrowly bladelike,
flat in cross section, usually green; underside
leaves much smaller
that lateral and upperside leaves.
4. Branchlets irregular,
with conspicuous annual bud constrictions; peduncles, if present
, regularly forked; strobili mostly 15-25 mm, lacking sterile tips. ..............................
..................................................................................2.
Diphasiastrum complanatum
4. Branchlets very
regularly fan-shaped, lacking conspicuous annual bud constrictions;
peduncles mostly branching abruptly at base to produce false whorl of strobili;
strobili mostly 20-35 mm, many with sterile tips............3.
Diphasiastrum digitatum
(Flora
of North America)