OCR Text |
Show 934 SELF-S'l'ERILE PLANTS. CHAP. IX. t:.h h B . .1 unless fertilised with ' . l f Sont razi ' , . native 1on1e 0 . . l· t either artificially or f distinct P an ' pollen rom a . b" ·l * Several plants were 1 b h mming- uc s. natural Y Y u _, d kept in the hothouse. . d f these seeus an . l raise rom . enr·ly jn the sr)nnbo·, anc d d fl wers ver v w · rrhey pro uce 0 . . " d . th pollen from h were fertihse ' soine Wl twenty oft em d with pollen from other fl wer an some l the same 0 ' 1 t . but not a single capsu e the same P an 8 ' flowers on . d et the stigmas twenty -seven hours was thus ptod~lce.' y f the I)ollen were penetrated by ft . the application o . n . a er At the salne time nineteen dowers the pollen-tube~.h ll n from a distinct plant, and were crossed wit .Po e les all abounding with these produced thuteen cabpesr~of 'capsules would have d A greater nun1 · . :fine see s. h . had not some of the nine-been produced by t e crossl, t which was afterwards fl · been on a P an teen owerbs f . some unknown cause completely . d to e rom . l t prove 1 . d Thus far these p an s sterile with pollel~ of any \:~n Brazil. but later in the behaved exactly hke those Inf M an' d in June they · tl l tter part o a Y ' season, 1n le a - d t a few spontaneously began to produce un er a ne on as this occurred, self-fertilised capsulesf. t"Al. s lso l'th their own po11en, . fl . were er 1 1sec w sixteen owers tainino· on an and these produced :fiv._e hcapsules,t.cmone I sel:cted by average 3 · 4 see d s. At t e same 1 d 1· ts grow-chance four capsules from t:e ~~c~v;r~als::n visited ing close by, the flowers o w ltc. l on an average bl b . d these con .an1ec by hum e- ees, an d . the naturally inter- 21· 5 seeds; so that the ~ee t~e !~elf-fertilised capsules crossed capsules to those In . . t . this case . as 100 to 16. The interesting poln In t J were . . unnaturally trea e is that these plants, which were d another by being grown in pots in a hothouse, un er ' -s .. 18,..,,2 p 22 and 181 ' "' 'Je naische Zeitschr. fiir N~ a t urwl.s s. 'B . Vll . ' • ' p. 441. CHAP. IX. SELF-STERILE PLANTS. 335 hemisphere, with a complete reversal of the seasons, were thus rendered slightly self-fertile, whereas they seem always to be co1npletely self-sterile in their native home. Senecio cruentus (greenhouse varieties, c01nmonly called Oinerarias, probably derived from several fruticose or herbaceous species much intercrossed* ).-Two purpleflowered varieties · were placed under a net in the greenhouse, and four corym bs on each were repeatedly brushed with flowers frorn the other plant, so that their stigmas were well covered with each other's pollen. Two of the eight corymbs thus treated produced very few seeds, but the other six produced on an average 41· 3 seeds per corymb, and these germinated well. The stigmas on four other corymbs on both plants were well smeared with pollen from the flowers on their own corymbs; these eight corymbs produced altogether ten extremely poor seeus, which proved incapable of genninating. I examined Inany flowers on both plants, and found the stigmas spontaneously covered with pollen; but they produced not a single seed. These plants were afterwards left uncovered in the san1e house where many other Cinerarias were in flower; and the flowers were frequently visited by bees. They then produced plenty of seed, but one of the two plants less than the other, as this species shows some tendency to be dimcious. The trial was repeated on another variety with white petals tipped with red. Many stigmas on two corymbs were covered with pollen from the foregoing purple variety, and these produced eleven and twenty- * I am much obliged to Mr. :M:oore and to Mr. Thisdtou Dver for giring me information with respect to the varieties on which I experimented. Mr. Moore be-lieves that Senecio cruentus, tussilaginis, and perhaps he1·ititri, maderenliis and popullfolius have all been more or less blended together in our Cineraria.s. |