278 DEPOSITION OF POLLEN. 



fig. 271 ^ left-hand flowers). A very noticeable change of position of stigmas and 

 anthers is also observed in flowers of the Gladiolus, the Hellebore (Helleborus), 

 the narrow-leaved Willow-herb {Epilohium angusti folium), various species of the 

 genus Honeysuckle (Lonicera aljngena, nigra, Xylosteum, &c.), also in the Figwort 

 {Scrophularia), species of the genus Penstemon and Cohcea, and finally in numerous 

 Solanaceae, as, for example, in the Deadly Nightshade (Atropa), the Henbane 

 (Hyoscyamus), Scopolia, and the Mandrake (Mandragora). Looking into the 

 newly-opened flower of the Mandrake (see fig. 279 ^) we see the spherical, sticky 

 stigma close below the entrance and exactly in the centre. The anthers, sur- 

 rounding it in a circle, are still unopened and placed against the inner wall of the 

 corolla. Since the mouth of the flower at this time is only slightly open, the 

 stamens are scarcely seen. Two days later the appearance of the same flower is 

 greatly altered. The style, bearing the stigma (now pollinated), has bent sideways 

 and impinges on the inner wall of the corolla, the anthers are pushed towards the 

 middle of the now widely-opened mouth, are covered with pollen, and have thus 

 changed places with the stigma (see fig. 279^). In the flowers composing the 

 umbels and capitula of many Umbellifers, Scabiouses, and Composites, the anthers 

 and stigmas may be said to change places in a certain sense, since the stigmas do 

 not mature until the neighbouring stamens have shrivelled up, or their anthers 

 have fallen off". In the heads of many Dipsaceae (Cephalaria, Succisa), and the 

 head-like umbels of the Eryngium, at first only pollen-covered anthers are seen 

 in all the flowers, and later only the stigma-bearing styles. The insects carry the 

 pollen away in masses from these inflorescences, so it is obvious that the deposition 

 must occur in the same manner, i.e. that an insect smothered in pollen, alighting 

 on an inflorescence with numerous stigma-bearing styles, and indulging in a series 

 of lively gyrations attaches its load in a few seconds to dozens of the sticky stigmas. 

 It is hardly necessary to state in detail that the small-pointed thorns, stiff 

 bristles, and other similar structures by which insects are shown the way into the 

 flower have the same significance for the deposition of pollen on the stigma as for 

 its removal from the anthers, and we can now merely refer to the descriptions on 

 pp. 250, 271, and 275. Only one other contrivance especially connected with the 

 deposition of pollen on the stigma, which acts as a remarkable sign-post, need be 

 mentioned here. In the flowers of many Cruciferse, e.g. those of Kernera saccatilis, 

 whose first and last stages of development are shown in figs. 267 "^ and 267 ^°, p. 249, 

 the petals at the time of opening are still small, stand erect, or are even somewhat 

 inclined inwards, almost touching the large stigma which nearly fills up the 

 entrance to the flower. Insects wishing to suck the honey at the base of the flower 

 are obliged by this position of the petals to push their probosces down close by the 

 stigma. Should the proboscis have been loaded with pollen in other flowers, this 

 will be inevitably deposited on the stigma. Later, when the stigma is withered, and 

 the floral-leaves have enlarged, the whole flower becomes inflated, the floral-leaves 

 becoming concav^e inwardly, the pollen-covered anthers become visible and access- 

 ible; and now when an insect directs its proboscis to the base it no longer touches 



