. Handbook of flower pollination : based upon Hermann Mu?ller's work 'The fertilisation of flowers by insects' . Fertilization of plants. 626 ANGIOSPERMAE—DICOTYLEDONES almost I cm. There are about 300 disk-florets. Each of these is 6-7 mm. long, of which 2 mm. is taken up by the ovary, 2^ by the corolla-tube, and 2 mm. by the bell of the corolla. In the first stage of anthesis the apposed stylar branches, covered with pollen, project from the bell; in the second stage the stigmatic inner surfaces of these branches protrude slightly. The diameter of the spinose pollen-grains is somewhat less t
. Handbook of flower pollination : based upon Hermann Mu?ller's work 'The fertilisation of flowers by insects' . Fertilization of plants. 626 ANGIOSPERMAE—DICOTYLEDONES almost I cm. There are about 300 disk-florets. Each of these is 6-7 mm. long, of which 2 mm. is taken up by the ovary, 2^ by the corolla-tube, and 2 mm. by the bell of the corolla. In the first stage of anthesis the apposed stylar branches, covered with pollen, project from the bell; in the second stage the stigmatic inner surfaces of these branches protrude slightly. The diameter of the spinose pollen-grains is somewhat less than that of the median groove that traverses the stigmatic surface. The stylar branches of the ray-florets bear shorter sweeping- hairs than those of the disk-florets. It is noteworthy that in this species the upper surface of the bell of the corolla in both kinds of floret is beset with countless microscopic papillae. Should insect-visits fail the pollen falls automatically on the expanded stigmatic surfaces. Warnstorf (Verh. bot. Ver., Berlin, xxxvii, 1896) describes the pollen-grains as yellow in colour, usually ellipsoidal, closely spinose, on an average 37-5 /* long and 30 m Fig. ao2. 1-7. Chrysanthemum segetunt^ L. (from nature), (i) Disk-floret in the first (male) stage; pollen is issuing from the anther-cylinder. (a) Do. in the second (female) stage. (3) Female ray-floret. (4) Tip of the style of a disk-floret in the first (male) stage (with branches apposed), enlarged. p^ stigmatic papillae. (5) Do. in the second (female) stage (with branches curving outwards), greatly enlarged. (6) Tip of the style of a ray-floret with diverging branches, enlarged. (7) Tip of stylar branch of a disk-floret, seen from within; in the middle is a groove mixed with pollen-grains; greatly enlarged. 8. Anthentis arvensis, L. (8) Tip of the style of a disk-floret with diverging and strongly recurve'd branches. 9. Tanacetum Parthenium^ L. (9) As 8, but branches much less divergent;
Size: 2047px × 1220px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, bookpublisheroxfor, bookyear1906
