In the
latter form the anthers stand above the stigma, and the style is very short and
thick; but the pistil varies a good deal in length, the stigma being either on a
level with the tips of the sepals or considerably beneath them. The foliaceous
stigma in the long-styled form is larger, with the expansions running farther
down the style, than in the other form. One of the most remarkable differences
between the two forms is that the anthers of the longer stamens in the short-
styled flowers are conspicuously longer than those of the shorter stamens in the
long-styled flowers. In the former the sub-triangular pollen-grains are larger;
the ratio between their breadth (measured from one angle to the middle of the
opposite side) and that of the grains from the long-styled flowers being about
100 to 75. Fritz Muller also informs me that the pollen of the short-styled
flowers has a bluish tint, whilst that of the long-styled is yellow. When we
treat of Lythrum salicaria we shall find a strongly marked contrast in the
colour of the pollen in two of the forms.
The three genera, Menyanthes, Limnanthemum, and Villarsia, now described,
constitute a well-marked sub-tribe of the Gentianeae. All the species, as far as
at present known, are heterostyled, and all inhabit aquatic or sub-aquatic
stations.
Forsythia suspensa (Oleaceae).
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