Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: CHAPTER II. THE PRINCIPLE OF NUMBER. Number — General Observations.—The first principle of Variation to be considered is that of the number of parts composing the different whorls of flowers. There are good reasons for considering that six whorls, consisting of five, four, three, or two parts each, as the case may be, should be regarded as the theoretically complete number of verticils of any flower. Anatomical investigations prove that the rule is for the pedicel to contain—at least, immediately below the flower,— if the latter be pentamerous, ten more or less distinct fibro- vascular cords, five of which belong to the sepals and five to the petals ; if it be hexamerons, there will be six cords, three for each whorl of the perianth. Each of these cords can give rise by branching, first, to a whorl of stamens and subsequently to a whorl of carpels, furnishing at least two marginal and one dorsal cord for each of the latter. In many flowers both whorls of stamens are present, and the androecium is then isomerous with the entire perianth. More often one whorl is arrested, and then it may be either one; but most usually it is the petaline. On the other hand, the calycine may not be developed as in Primroses, Bhamnus, etc. The absence of the petaline stamens is possibly attributable to the law of compensation, in consequence of the enhanced growth of the corolla, the petals thereby abstracting the nourishment that would be required by the stamens superposed to them. That the number of staminal whorls should be two in verticillate flowers, i.e., equal to the perianth, is apparent from the fact that two whorls prevail in Monocotyledons and are not at all uncommon in Dicotyledons ; and when the petaline whorl alone exists, as in Primulacece and Myrsinece, calycine stami...