. A manual of botany. Botany. 146 MANUAL OF BOTANY outgrowth or placenta, and at the base of the latter there are two ovules. Similar cones occur among the Cj'cads, some of which have both miorosporophylls and megasporophylls so arranged. Spiral phyllotaxis also occurs in the Angiosperms in certain families where the normal phyllotaxis of the flower is whorled, though it is less common than the other cases of interference with typical symmetry. There are two degrees in which it exists, a. The whole of the floral leaves may be arranged spirally, as in the Water-Uly {NymphcBa) {fig. 276). Here t
. A manual of botany. Botany. 146 MANUAL OF BOTANY outgrowth or placenta, and at the base of the latter there are two ovules. Similar cones occur among the Cj'cads, some of which have both miorosporophylls and megasporophylls so arranged. Spiral phyllotaxis also occurs in the Angiosperms in certain families where the normal phyllotaxis of the flower is whorled, though it is less common than the other cases of interference with typical symmetry. There are two degrees in which it exists, a. The whole of the floral leaves may be arranged spirally, as in the Water-Uly {NymphcBa) {fig. 276). Here the members of the separate whorls show gradual transition from one form, to the next. The outer leaves are green and sepa- loid ; as we pass inwards their green hue is gradually replaced Fig. Fiq. 276. Mower of the White Water-lily {Ntjirtplma alba) reduced in size. After Jussieu. c, c, c, c. The sepals. /i,^,2j,/i. Petals. '.Stamens. Tlie pacts ou the right show the gradual transition from the sepals, c, to the petals, p, and from these organs to the stamens, e. The stamens from 1 to 5 arL- gradually more distinctive. by white, till they are evident petals; there is a similar tran- sition from petals to stamens, the leaves becoming narrower and indications of anthers appearing at their summits, till the definite staminal form is reached. Such flowers are known as acyclic, h. The perianth may be in whorls and the sporophylls arranged spirally. This is the case in the Buttercup, where there are two series of spirals, the androeoium and gyncecium. They do not show a transition to each other as in the former case. The flower of the Buttercup is termed hemicyclic. Some- times the whorls of the perianth are not true ones, but result from a condensed spiral. This may be seen in such corollas as have a quincuncial sestivation (see page 210). 8. Metamorphosis of Parts of the Flower.—A modification. Please note that these images are extracted from scanned page images that may ha
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