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310
somes in an equal multiple of 7, must be supposed to be originated
(either directly or in a preceding generation) from seeds produced
by fertilizalion.
22. From the chromosome sets it can be concluded (compare
point 20), which species produce apomictical seeds. Such roses
are all examined species belonging to the section Caninae (Caninae,
Afzelianae, Villosae, Tomentosae, Rubiginosae, Stylosae, Junzillianae,
Rubrifoliae etc.)
23. As to the kind of apomixis here present, I am not yet clear
on that point. However, it is not to be thought of as apogamy,
all the found spindles of the first division of the embryo-sac mother
cells having the described character of reduction. I have not found
any positive evidence for apospory. As to wether the apomictical
embryos are formed by nuzellar buds, I cannot say now, the suitable
stages being lacking in my material.” The investigations regarding
this point are to be continued.
24. All species and forms investigated belonging to the
section Caninae, i. e. the majority of the examined roses ori-
ginated in Europe, North Africa and West Asia, are very
ancient hybrids representing the F,-generation, which,
ever since its origin thousands years ago, has been main-
tained owing to apomictical reproduction.
25. The anorthoploid bushes (with diverging chromosome sets)
mentioned in point 21 represent F, or any later generation of
crosses between two F,-specimens belonging to different species.
26.- The power of producing seeds apomictically probably was
gained in connection with these ancient crosses.
27. For the explaining of the peculiar chromosome conditions
in the Canina-section it is necessary to assume the existence of
some normally sexual roses with higher chromosome numbers than
found by me, namely octoploid (x = 28) and decaploid (x = 35)
forms. From crosses between diploid (x — 7) and _ hexaploid
(x = 21) forms the tetraploid villosa and’ rubrifolia (7 bivalents +
14 singles = 28) arose. The parents of the pentaploid roses (7
bivalents + 21 singles = 35) have likely been diploid (x = 7) and
octoploid (x = 28) forms, and the parents of the hexaploid (7
bivalent + 28 singles = 42) diploid (x — 7) and decaploid (x = 35)
races. It would be very interesting to know, wether normally
sexual roses with higher chromosome numbers than the hexaploid
(x = 21) still exist.
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