434 M. A. Kerner on the Protection of Pollen 



of the sun, and close in the course of the evening. Their 

 usual visitors are of course the crepuscular insects ; and to 

 attract these some are clothed in brilliant colours (nightshade 

 and several Oenotheras), whilst others have very dull colours 

 but exhale a penetrating perfume, which is insensible during 

 the day {Pelargonium triste, Hesperis tristis, Nyctanthes arbor- 

 tristis). But these cases are quite exceptional, and the great 

 majority of flowers with periodical movements open during the 

 brightest hours of the day ; the petals, in closing again, resume 

 the position they occupied in the bud, and thus completely 

 protect the stamens and the style. 



Where it is by means of curvatures of the floral axis that 

 fecundation is ensured, the perianth must be brought into such 

 a position as to form a protective roof for the reproductive 

 organs. Its form, and also the degree of curvature, depend of 

 course greatly upon the length of the stamens : where, as in 

 the lily of the valley, these are quite short, a slightly developed 

 perianth and a simple lateral inclination suffice to attain the 

 desired object ; but where, as in the fuchsia, the anthers are 

 borne upon long filaments, the perianth is much broader and 

 spread out like a wheel, and the flower becomes completely 

 pendent. 



All degrees of curvature are met with in nature : sometimes 

 the phenomenon is already perceptible in the bud (Soldanella) ; 

 in other cases it is manifested only at the moment of flowering. 

 When once fecundation is effected the young fruit usually 

 becomes erected, at least if it is not of a fleshy nature, and 

 consequently too heavy to be carried up by the tension of the 

 tissues of the peduncle (Fuchsia, many Solana). 



It is sometimes the case that the curvature of the axis, like 

 the closing of the perianth, is periodical. Thus the flower of 

 Oxalis acetosella, which is completely erect during the day, 

 describes an arc of more than 100 degrees at the moment when 

 the sun sets, and finally has its opening directed towards the 

 ground. The periodical changes in the tension of the tissues 

 of the peduncle required by this movement occur in many other 

 plants under the influence of exterior excitements, repeated 

 shocks, &c. ; and many flowers which are usually erect become 

 recurved towards the earth, and thus protect their stamens 

 when they are shaken by the wind or disturbed by the repeated 

 shocks of drops of rain (many Composite, tulips, anemones, 

 Ranunculus, poppies). 



Lastly, in those compound inflorescences of which the axis 

 is twisted, as in the Boraginese and some other families, de- 

 velopment brings the flowers successively into all sorts of 



