STAMENS. 93 



doors. This is known as valvate dehiscence. It is met with generally in 

 Berberidaceae (e.g. Berberis and Epimedium) and Lauracese. In the Bay Laurel, 

 Camphor, and Cinnamon Trees (Laurus nobilis, Camphora officinalis, and Cinna- 

 momum) and Nyctandra (fig. 216 ^®) are found little apertures on one side of the 

 stamen, each with its trap-door or valve, which is raised up in dry, but shut 

 down in wet weather. The anthers of Mimulus, Galeopsis, and Ga/roinia 

 (figs. 216 ^^ and 216 ^^) resemble little tubs or boxes, which on opening raise their 

 lid-like valves. 



The dehiscence of the anthers in many plants is accompanied by yet other 

 changes. The two anther-halves may become partly separated from their attach- 

 ments and become twisted or diverge at right angles. If the anther-halves 

 separate at the base only, as in Convolvulus, Gentiana, and Menyanthes, the 

 anther assumes the form of an arrow-head; if they separate both above and 

 below, and at the same time become somewhat bent, we have an X-shaped anther, 

 found in many Grasses. In many Crucifers (Diplotaxis, Sina/pis, &c.) the anthers 

 become spirally twisted after dehiscence, a feature very pronounced in the 

 Centaury (JErythrcea, figs. 216 ^^ and 216 ^^). A very striking phenomenon is 

 the shortening which not a few anthers with longitudinal slits undergo after 

 dehiscence. The anthers of most Liliaceous plants are long and linear; they 

 dehisce by means of slits from above downwards. In the course of a few hours 

 they are transformed into globular bodies, covered with pollen. In Gagea lutea 

 these balls have a diameter only one-third of the previous length of the anther, 

 whilst the anthers of the Crown Imperial (Fritillaria imperialis) shorten from 

 20 to 10, those of Narcissus poeticus from 11 to 4, and those of Scilla bifolia 

 from 2 to 1 millimetres. 



Each one of the various occurrences which accompany or succeed dehiscence 

 depends upon some structural character of the anther-wall. The relations are 

 simplest in those anthers which open by means of pores. The pores arise from 

 the absorption of limited portions of the wall. Further changes, such as the 

 shrivelling or shortening of the anther, or the expanding of the apertures, do 

 not occur. There is a corresponding simplicity of the tissues of the anther-wall. 

 Similarly, in anthers (e.g. Orchids) in which a splitting arises along a previously- 

 indicated line, or in consequence of the absorption of a row of cells, no peculiarities 

 are noticeable on the wall. But where slits with movable lips and valves are 

 developed, cells of characteristic structure are present, which may be termed 

 the contractile cells. One series consists of more or less cubical cells, and exhibit, 

 on portions of their walls, fibrous or rod-shaped thickenings. The wall of one of 

 these cells directed towards the cavity of the anther is equally thickened, that 

 towards the outside is thin and delicate, easily folded, and destitute of thicken- 

 ings. The side-walls, however, are characteristically strengthened by rod-like 

 thickenings. The thickenings present may be compared to a hand, in the position 

 usually employed in grasping an apple; the palm corresponds to the strongly- 

 thickened inner wall, and the fingers to the tapering, rod-like thickenings. of the 



