PROTECTION OF POLLEN. 



121 



alpina, A. carniolica, &c.), it is the stalks of the umbels, and in some Cruciferous 

 plants (e.g. Draba aizoides, Arabia Turrita, Sisymbrium Thalianum), the axes 

 of the racemes. The above-mentioned Scabious and Composites exhibit a periodic 

 inversion of the entire inflorescence in consequence of the inflection of the axis, 

 and the radiating ligulate florets set round the margin of the capitulum serve 

 to shelter the pollen of the central florets. Similarly in the Umbellifers named, 

 the involucres of the separate umbels, being comparatively large, act in the same 

 way. The fact is also worth notice that in some Willow-herbs (e.g. Epilobium 



Fig. 225. Protection of Pollen. 



Flowers of the Herb-Robert (Geranium Robertianum) in the daytime ; the pedicels erect. 2 The same plant with its flowers 

 pendent on curved pedicels, the position assumed during the night and in wet weather, s Bell-flower (Campanula 

 patula) by day ; the flower on erect pedicel. * Flower of the same plant inverted for the night or for wet weather, the 

 pedicel being curved. 6 Capitulum of a Scabious (Scabiosa lucida) in the daytime; the peduncle erect. 6 Capitulum of 

 the same plant at night or during rain, the peduncle curved and the capitulum inverted. 



hirsutum, E. montanum, E. roseum), the flower-stalks themselves do not bend, 

 but the long stalk-like inferior ovaries curve downward and straighten out 

 again, periodically causing the flowers, which are of a flat salver shape, to 

 alternate between a pendent and an erect position. The inflection of flower- 

 stalks, or, of their substitutes, the ovaries, ceases as soon as the pollen of the 

 flowers concerned has been removed by one means or another, and a shelter for 

 it is no longer needful. The flower-stalks of Saxifraga Huetiana only con- 

 tinue to bend so long as the anthers in the flowers they support are covered 

 with pollen, and the long ovaries of the Willow-herbs mentioned above 

 only curve towards the earth on two successive evenings; the third evening, 



