I may add that I also possessed some long-styled plants of this
species: one was covered by a net, and it set spontaneously a few capsules,
though extremely few compared with those produced by a plant growing by itself,
but exposed to the visits of bees.
With most of the species of Oxalis the short-styled form seems to be the most
sterile of the three forms, when these are illegitimately fertilised; and I will
add two other cases to those already given. I fertilised 29 short-styled flowers
of O. compressa with pollen from their own two sets of stamens (the pollen-
grains of which differ in diameter as 100 and 83), and not one produced a
capsule. I formerly cultivated during several years the short-styled form of a
species purchased under the name of O. Bowii (but I have some doubts whether it
was rightly named), and fertilised many flowers with their own two kinds of
pollen, which differ in diameter in the usual manner, but never got a single
seed. On the other hand, Hildebrand says that the short-styled form of O.
Deppei, growing by itself, yields plenty of seed; but it is not positively known
that this species is heterostyled; and the pollen-grains from the two sets of
anthers do not differ in diameter.
Some facts communicated to me by Fritz Muller afford excellent evidence of the
utter sterility of one of the forms of certain trimorphic species of Oxalis,
when growing isolated.
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