. Handbook of flower pollination : based upon Hermann Mu?ller's work 'The fertilisation of flowers by insects' . Fertilization of plants. CAMPANULA CEAE 19 Conspicuousness is greatly enhanced by aggregation of the usually blue or violet flowers into rounded, ovoid, or elongated heads, and the frequency of insect-visits is generally proportional to the size of the heads. Kirchner (Jahreshefte Ver. Natk., Stuttgart, liii, 1897, pp. 219-20) has empha- sized the fact that the above description, abstracted from Hermann Miiller, only appUes to species belonging to the section Hedranthum G. Don, in w
. Handbook of flower pollination : based upon Hermann Mu?ller's work 'The fertilisation of flowers by insects' . Fertilization of plants. CAMPANULA CEAE 19 Conspicuousness is greatly enhanced by aggregation of the usually blue or violet flowers into rounded, ovoid, or elongated heads, and the frequency of insect-visits is generally proportional to the size of the heads. Kirchner (Jahreshefte Ver. Natk., Stuttgart, liii, 1897, pp. 219-20) has empha- sized the fact that the above description, abstracted from Hermann Miiller, only appUes to species belonging to the section Hedranthum G. Don, in which the flowers are sessile and the corolla-lobes gradually become separate from base to tip in the course of anthesis. The flowers of the section Synotoma G. Don are also Fig. 213. Pliy/euma, L. (after Herm. Miiller). A. Young flower-bu(3 of Phyteuma Michelii, after removal of the corolla and one stamen. B. Flower in the first (male) sta^e. C. Ditto, in the second (female) stage (X 7). a, anthers; ca, calyx; co, corolla ;y/2, stylar brush (sweeping-hairs);_/?, filaments; p, corolla-lobes; po, pollen ; s, teeth of calyx; sd, nectar-covers ; st, stigmas. In the sub-genera Podanthum Boiss., Petromarula Ve}il., and Cylindrocarpa Regel, the inflorescences are panicles or racemes, so that their flowers differ very essentially in form and mechanism from those which are more closely associated. This is the case, for instance, with the next species. 1737. P. canescens Waldst. et Kit. (Kirchner, op. cit., pp. 219-20.)—This species belongs to the section Podanlhum. Kirchner has investigated it in the Hohenheim Botanic Garden. The flowers are arranged in a long loose raceme, and their mechanism is closely related to that of Campanula. The calyx-teeth are green in colour, subulate, and 5 mm. in length. The five (sometimes four) petals are 10-15 "^"i- lon&> ^^^i^ 2-2 J mm. broad, and scarcely united at their bases. They diverge almost in the same plane to form a
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