The pollen-grains of the short-styled form, according to
Hildebrand, are 7 divisions of the micrometer in length and 5 in breadth;
whereas those of the long-styled are only 4 in length and 3 in breadth. (1/10.
After the appearance of my paper this author published some excellent
observations on the present species 'Botanische Zeitung' January 1, 1864, and he
shows that I erred greatly about the size of the pollen-grains in the two forms.
I suppose that by mistake I measured twice over pollen-grains from the same
form.) The grains, therefore, of the short-styled are to those of the long-
styled in length as 100 to 57. Hildebrand also remarked, as I had done in the
case of P. veris, that the smaller grains from the long-styled are much more
transparent than the larger ones from the short-styled form. We shall hereafter
see that this cultivated plant varies much in its dimorphic condition and is
often equal-styled. Some individuals may be said to be sub-heterostyled; thus in
two white-flowered plants the pistil projected above the stamens, but in one of
them it was longer and had a more elongated and rougher stigma, than in the
other; and the pollen-grains from the latter were to those from the plant with a
more elongated pistil only as 100 to 88 in diameter, instead of as 100 to 57.
The corolla of the long-styled and short-styled form differs in shape, in the
same manner as in P.
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