See also for another case ibid page 845.)
Lathyrus odoratus.
Almost everyone who has studied the structure of papilionaceous flowers
has been convinced that they are specially adapted for
cross-fertilisation, although many of the species are likewise capable
of self-fertilisation. The case therefore of Lathyrus odoratus or the
sweet-pea is curious, for in this country it seems invariably to
fertilise itself. I conclude that this is so, as five varieties,
differing greatly in the colour of their flowers but in no other
respect, are commonly sold and come true; yet on inquiry from two great
raisers of seed for sale, I find that they take no precautions to insure
purity--the five varieties being habitually grown close together. (5/11.
See Mr. W. Earley in 'Nature' 1872 page 242, to the same effect. He
once, however, saw bees visiting the flowers, and supposed that on this
occasion they would have been intercrossed.) I have myself purposely
made similar trials with the same result. Although the varieties always
come true, yet, as we shall presently see, one of the five well-known
varieties occasionally gives birth to another, which exhibits all its
usual characters. Owing to this curious fact, and to the darker-coloured
varieties being the most productive, these increase, to the exclusion of
the others, as I was informed by the late Mr. Masters, if there be no
selection.
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