FLOWER-GROUPS 65 



As I have pointed out in my 'Grundriss der Blutenbiologie ' (p. 9, note), 

 Henn. Muller's nine classes of flowers may readily be extended to twelve, inas- 

 much as social flowers with exposed nectar may be distinguished from those 

 with partially concealed nectar. For these two groups the symbols A' and AB' 

 would be appropriate. The compound umbels of the Umbelliferae (especially 

 of those with radiating marginal flowers), and the cymes (especially again those 

 with neuter enlarged marginal flowers, e. g. those of Viburnum Opulus) also form 

 an oecological unity, comparable with, e.g., the capitula of the Compositae, for 

 like these they serve as a whole to entice insects, and also secure simultaneous 

 pollination of numerous flowers by the passage of insects over the one continuous 

 surface formed by the inflorescence. As examples of the class AB', the corymbs of 

 some Cruciferae may be taken, especially those of Iberis and Teesdalia, because in 

 these the flowers at the margin of the inflorescence are larger than those in the 

 middle. Accordingly, the following classes of flowers would result : — W (i. e. wind- 

 pollinated or anemophilous flowers), Po, A, A', AB, AB', B, B', H, F, D, Kl. 



C. Verhoeff, in his work 'Blumen und Insekten auf der Insel Norderney ' 

 (Nova Acta Leop., Halle, Ixi, 1894, pp. 174 and 175), attempts to change the 

 classification of Herm. Muller in accordance with the comparatively few plants in- 

 vestigated by him with regard to their flower pollination on the island of Norderney '. 

 He distinguishes : — 



1. Wind-pollinated Flowers (W) : no adaptation to insects, but occasionally 

 visited by them. Hippophae rhamnoides. 



2. Adinomorphous Pollen-flowers {Po K) : pollen adhesive, corolla usually coloured, 

 no nectar. Cochlearia anglica, Helianthemum, Rosa, Polygonum aviculare. 



3. Zygomorphous Pollen-flowers iVo'B): general character as before. Sarothamnus 

 scoparius. 



4. Neclar Flowers {^t): no coloured perianth-leaves or petals, producing nectar, 

 sticky pollen. Salix. 



5. Flowers with exposed nectar, but not social (A) : brightly coloured perianth 

 leaves or petals, nectar exposed, pollen sticky. Actinomorphous. Ranunculus 

 Flammula, Batrachium, Honckenya, Parnassia. 



6. Flowers adapted in the same way but associated in crowded small-flowered 

 societies (AG). Most of the Rubiaceae and Umbelliferae. 



7. Flowers with partly concealed nectar; quite or almost actinomorphous (AB) : 

 Ranunculus acris, repens, sceleratus ; Cardamine, Stenophragma, Brassica, Capsella, 

 Sisymbrium, Cerastium, Rubus, Sedum, Glaux, Polygonum Persicaria. 



8. Flowers with completely concealed nectar; sometimes actinomorphous, some- 

 times zygomorphous (B) : pollen not concealed. Silene, Lychnis, Erodium, Epilobium, 

 Vaccinium, Calluna, Pyrola (a specially adapted form, according to Verhoeff), 

 Myosotis, Veronica, Euphrasia, Mentha, Stachys, Armeria, Orchis, Asparagus. 



9. Flowers with nectar equally well concealed, but the flowers united into capitulate 

 societies (BG) : pollen not concealed. Most Compositae, and Jasione— the latter 

 with nectar not quite so deeply hidden. 



See note on preceding page. 

 F 



