The origin of floral structures through insect and other agencies . anged quincuncially in estivation (, a) ; and when they are not so they can be referred to * I consulted the first volume of the Genera Plantarum for thispurpose, which embraces the Thalamijlorcc and Galyciflorcc. THE PRINCIPLE OF NUMBER. 15 it, as I have explained elsewhere : * thus Fig. 3 shows howthe varieties of imbricate aestivations are deducible fromthe |- type (a), bj shifting the edge of the 2nd member underthe 4th (b, vexillary ), the 3rd under the Sth (c, imbricateproper ), and the 1st under the 3rd (d, contort
The origin of floral structures through insect and other agencies . anged quincuncially in estivation (, a) ; and when they are not so they can be referred to * I consulted the first volume of the Genera Plantarum for thispurpose, which embraces the Thalamijlorcc and Galyciflorcc. THE PRINCIPLE OF NUMBER. 15 it, as I have explained elsewhere : * thus Fig. 3 shows howthe varieties of imbricate aestivations are deducible fromthe |- type (a), bj shifting the edge of the 2nd member underthe 4th (b, vexillary ), the 3rd under the Sth (c, imbricateproper ), and the 1st under the 3rd (d, contorted ). Similarly ternary ortrimerous whorls are almost universalamongst flowers of Monocotyledons, and the ^ type of phyllo-taxis is equally common in the foliage. It has been seentliat the ^ type cannot be deduced from opposite leaves, andconsequently never occurs, as ft^r as I know, amongst thefoliage of Dicotyledons. The comparatively few genera inthis class with ternary flowers is therefore in accordancewith the views herein expressed; and where they occur, as. a 6 o Fig. 3.—Floral iEstivaticns. in Berberis, there are special features which lead one tobelieve they are not due to the ^ type at all, but to thebreaking up of a high continuous spiral into groups ofthrees, as will be explained hereafter. If, however, we take a theoretical departure from asingle cotyledon, as occurs in Monocotyledons, then the nextleaf can be at either of the limiting positions of the angulardistances of 180° or 120°, but not less; for if it were lessthan 120°, there would be four leaves in any projectedcircle, and this would immediately introduce a member ofthe series ^, ^, f, etc., as shown above. The consequence is * See my papei-, On the Origin of Floral Estivations, Trans. Lin. Soc,2ncl series, Botany, vol. i. p. 177. 13 THE STRUCTLTRE OF FLOWERS. tliat the ^ and ^ types are exceedingly common in the foliageof ^lonocotjdedons, while the f, as far as I am aware, isentirely wanting in that
Size: 2973px × 841px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1880, booksubjectfertili, bookyear1888
