Trees with yellow-brown hairy twigs. Leaves rounded, 1-2 cm, with 2 white
stomatal bands beneath. Female cones ovoid, 2.5cm.
Tsuga canadensis in eastern Canada and USA east of the Mississippi,
T. caroliniana in the USA Southeast,
T. heterophylla in western Canada and Pacific Northwest of USA.
Pollen light micrograph:
The morphology of the Tsuga heterophylla type is unique, and the
beginning palynologist might be surprised that it is classified
as "saccate" or "vesiculate" pollen, because it is so different from
the bisaccate pollen of other Pinaceae. However, the encircling "frill" or "fringe"
is homologous with the paired sacci of pine, spruce, and fir. And, its rough -
undulating sculpturing is similar to the anti-saccus surface of those grains.
To me, the frill is reminiscent of a medieval monk's tonsure.
The morphology of Tsuga canadensis is very similar to T. heterophylla.
It is 70 to 80 µm in diameter and is essentially spherical. However, the
mountain hemlock (Tsuga mertensiana) of western North America is
small and bissacate.
There are several species of Asian hemlocks. Tsuga forrestii is illustrated
in Erdtman (1957) as both monosaccate and bisaccate, but
T. chinensis, T. diversifolia, T. dumosa, T. pattoniana, T. sieboldii, and T. yunnanensis
are not descirbed in that text.
Pollen scanning electron micrograph (SEM)
Production and Dispersal:
Wind pollinated with moderate production moderate dispersal