366 AUTOGAMY. 



they rest in the last stage against the lateral edges of the stigmas. This process is 

 very common in plants of the order Solanacese (Hyoscyamus, Lycium, Nicotiava 

 Physalis, Scopolia), and it has also been observed in Gentianaceae (e.g. Erythroea 

 pulckella, Gentiana campestris, G. glacialis). In some of these plants the elonga- 

 tion undergone by the corolla-tube is very considerable as compared with the size 

 of the flower. In the American Tobacco plant (Nicotiana Tabacwm) it amounts to 

 nearly J cm., whilst in the little Centaury {Erythroea) it is only 2 mm. The elon- 

 gation of the corolla-tube is accompanied in most instances by a stretching of the 

 filaments. In consequence of this combined growth the anthers are, in the case of 

 the short-styled flowers of Lycium barbarum, raised ^ cm. in 24 hours. In the 

 Henbane {HyoscyaTnus niger) the anthers are 7 mm. lower than the stigma in the 

 morning when the flower is nearly open, but by the evening of the same day the 

 simultaneous elongation of the corolla-tube and of the stamens adnate to it has 

 raised the anthers to the level of the stigma and pressed them upon it. It is scarcely 

 necessary to mention that in these plants, which are all protogynous, cross-fertiliza- 

 tion is possible in the first part of the flowering period, and it is as a matter of fact 

 very frequently effected through the intervention of insects. 



A very curious variety of the phenomenon in question is exhibited by the large- 

 flowered species of the Eyebright genus {Euphrasia Rostkoviana, E. versicolor, 

 E. speciosa), and by the allied Yellow Rattles {Rhinanthus angustifolius and R. 

 hirsutus). The flowers of these plants face sideways, and the corolla has a tri-lohed 

 under lip and a bi-lobed helmet-shaped upper lip. Four stamens of the pollen- 

 sprinkling type, which we have compared to sugar-tongs, are adnate to the corolla- 

 tube. The anthers are concealed beneath the upper lip; the long filiform style is 

 in the shape of the letter S and lies above the anthers, and when the flower is first 

 open it projects considerably beyond them (see fig. 277*, p. 273). Stigma and 

 anthers are then so placed as to make it inevitable that insects which enter the 

 flower shall first touch the stigma, and the next moment become dusted with a 

 shower of pollen from the anthers. If several blossoms are visited in succession 

 cross-fertilization is certain to take place. If, however, insects stop away, the tube 

 of the corolla elongates and carries up with it the epipetalous stamens. As the 

 style retains its original length, the terminal stigma, which hitherto has projected in 

 front of the anthers, now rests by the side of the anthers or just above them. Thus 

 the stigma is in a sense overtaken by the anthers. In the large-flowered species of 

 Eyebright the tense style then presses upon the anthers, forces them asunder, and, 

 sinking down, brings its stigma between the anther- valves, where it cannot fail to 

 get coated with the pollen of which they are still full. In the species of Yellow 

 Rattle above mentioned, the stamens become flaccid towards the end of the flower's 

 period of bloom and the pollen falls out and is left sticking to the hairs of the 

 anthers or to the involute folds of the corolla, so that the style in brushing by 

 usually removes it. 



It is much less common for the calyx to play this part in bringing about 

 autogamy. Tellima grandiflora, a North American Saxifragacea, is the only ease 



