With respect to the pistil, the style may be almost thrice as long in the one
form as in the other. In Oxalis it sometimes differs in hairiness in the three
forms. In Linum the pistils either diverge and pass out between the filaments,
or stand nearly upright and parallel to them. The stigmas in the two forms often
differ much in size and shape, and more especially in the length and thickness
of their papillae; so that the surface may be rough or quite smooth. Owing to
the rotation of the styles, the papillose surface of the stigma is turned
outwards in one form of Linum perenne, and inwards in the other form. In flowers
of the same age of Primula veris the ovules are larger in the long-styled than
in the short-styled form. The seeds produced by the two or three forms often
differ in number, and sometimes in size and weight; thus, five seeds from the
long-styled form of Lythrum salicaria equal in weight six from the mid-styled
and seven from the short-styled form. Lastly, short-styled plants of Pulmonaria
officinalis bear a larger number of flowers, and these set a larger proportional
number of fruit, which however yield a lower average number of seed, than the
long-styled plants. With heterostyled plants we thus see in how many and in what
important characters the forms of the same undoubted species often differ from
one another--characters which with ordinary plants would be amply sufficient to
distinguish species of the same genus.
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