154 



DISPERSION OF POLLEN BY ANIMALS. 



chrysalis condition. One may see, frequently, on examining the ripe fruit-capsules 

 of the Catchflies, the perforations by which the moth-larvse have gained their 

 freedom. If the caterpillars of Dianthoecia devoured all the seeds in the ovaries, 

 the species of plants frequented by them would derive no benefit, but, on the con- 

 trary, an injury from their visits. Owing to the large number of ovules, howevei-, 

 they are very seldom completely destroyed, and even if all the seeds in one of the 

 capsules were to be consumed there would always be other capsules in the same 

 plant which would develop plenty of seeds capable of germination. The majorit}^ 

 of the Caryophyllaceous species here in question, the Nottingham Catchfly {Silene 

 nutans, see figs. 238 and 239) amongst the rest, flower at night, their blossoms 



opening at dusk, remaining expanded all night, 

 and closing at sunrise. This is repeated in 

 the case of each flower at least three times. 

 On the first evening the petals which have 

 hitherto been rolled up and folded in the 

 bud, spread themselves out in rays and 

 bend somewhat back (fig. 239); five anthers 

 are rapidly exserted from the middle of 

 the flower, and these soon afterwards de- 

 hisce, become covered with adhesive pollen, 

 and remain the whole night in that condi- 

 tion. In the course of the following morning 

 the filiform filaments bearing the anthers 

 belonging to the outer circle of stamens 

 bend back, and the anthers fall oft' or, less 

 commonly, are left hanging to the ends 

 of the reflexed filaments in the form of 

 empty shrivelled sacs. The next evening 

 the second whorl of stamens included in these flowers comes into play, and just 

 in the same manner as before, five anthers, which dehisce at nightfall, are exserted 

 from the mouth of the flower and expose their pollen. The third day these 

 stamens likewise bend back and usually let their anthers drop, and when dusk sets 

 in the long velvety S-shaped stigmas, which have till then been concealed inside the 

 flower, are pushed out. Certain changes of position aflecting the petals proceed 

 simultaneously with these mutations. It has already been mentioned that the 

 petals rolled up in the bud unfold on the first night, and assume a stellate and re- 

 flexed attitude. At this time also the flowers emit a delicate perfume like that of 

 hyacinths, which attracts a large number of nocturnal insects, but only lasts from 

 8 o'clock in the evening till about 3 a.m. At daybreak the petals begin to roll up 

 again, the operation taking place faster when the temperature is moderately high 

 and the sky clear than when the weather is cold and the sky overcast. In the pro- 

 cess of involution the petals fall into longitudinal folds and become wrinkled and 

 grooved, so that they hang like five crumpled bags round the mouth of the flower, and 



Fig. 238.— The Nottingliam Catchfly {Silene nutans) 

 in the daytime. 



