082 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



spread out one above the other and facing the front or lip. If a slight 

 touch be given along the line of junction they immediately close up. 



A similar movable stigma occurs both in Salpiglossis and even in an 

 allied family, Bignoniacece, for it occurs in Tecoma and Caialpa. 



In all cases of movements of floral organs the immediate cause 

 appears to be the same as in Dioncea and Mimosa, in that it is by a loss 

 of turgidity on one side of the organ, so that it contracts ; and the other 

 side, not having done so, of course makes the organ move in the direction 

 of the contracted side. 



If it be further asked, why does the protoplasm lose its water on being 

 touched, or, rather, on " feeling" the touch, so to say, through the cell- 

 wall, it is impossible to reply, because we do not know what life is. A 

 similar question might be asked. Why does the foot draw itself away, 

 if the sole be irritated, in spite of all volition at our disposal to 

 prevent it ? 



Levers. — The following descriptions will illustrate some cases of the.se 

 mechanical powers. The first kind is that in which the fulcrum is 



between the power and the weigJit or resistance, as in resting a poker 

 on the bars (the fulcrum) to raise the coals (the weight) in a fire. An 

 instance of this kind will be found in the genus Salvia (fig. 296). 

 The flower has two stamens adherent to the corolla by very short 

 filaments, each of which carries two anthers, separated by a long curved 

 '^connective.'' These stand in a vertical plane, the upper anther-cell 

 produces pollen, but the lower one has usually none, and forms a spoon- 

 shaped end. The connective forms an arc of a circle, but is attached to 

 the filament at a point (upon which it oscillates) much nearer the lower 

 end than the upper one (see figure). The result is that it forms a lever 

 of which, on depressing the short " arm " below, the long arm swings 

 through a considerable distance ; and if it be supposed that a bee, on 

 alighting on the lip in front and striking the empty anther-cells below, 

 has depressed it in searching for honey, the upper anther-cells come 

 down into the position shown in the figure, and deposit their pollen on 

 the .bee's back. The forked stigma projects forward in a suitable position 



Fig. 296. — Anterior portion and 

 stamens of Salvia, showing ar- 

 rangement of stamens and their 

 action. 



Fig. 297. — Vert. sect. (A) of unopened, 

 pendulous flower of Strawberry 

 tree {Arbutus Unedo), showing 

 young anthers adhering by their 

 tips to the style ; (B) stamens and 

 style of fully expanded flower, 

 showing anthers now inverted. 



