MOTIONS OF SEED-VESSELS. 267 



419. Some of the most interesting among the vegetable 

 movements are those concerned in the deposition of the seed. 

 The Balsam termed Impatlens noli-me-tangere has a seed-vessel 

 or capsule, formed of five divisions or valves ; which, when the 

 seed is ripe, suddenly separate from one another and curl in- 

 wards, scattering the seed to some distance. Now an examina- 

 tion of the tissue of these valves shows, that their outer part 

 consists of much larger cells than the inner, and that the fluid 

 contained in it is the densest. By the laws of Endosmose 

 (. 118), therefore, the fluids contained in the tissue of the 

 interior will have a tendency to pass towards the outside, and 

 will distend its vesicles still more. This distension of the out- 

 side layer will manifestly give the valves a tendency to curl 

 inwards ; just as when two thin plates of metal, which expand 

 unequally by heat, are soldered together, and, heat being applied, 

 the compound plate bends towards the side which expands least. 

 This tendency continues to increase up to the time when the 

 seed is ripe ; and it is then so powerful as to cause the separa- 

 tion of the valves from each other, and to occasion the rolling 

 inwards of each. Now it has been found that, if the valves be 

 placed in a fluid more dense than that which the valves contain, 

 such as syrup or gum-water, the fluid will be drawn off from 

 their cells, according to the same law of Endosmose ; and the 

 cells on the exterior will be emptied soonest, on account of 'their 

 being larger and fuller than the others ; so that the valves be- 

 come straight, and even curl outwards. But if they be put into 

 water, the Endosmose, still taking place towards the side on 

 which the fluid is densest, namely the interior of the cells, 

 will distend them still more, and will cause the valves to curl 

 inwards more powerfully than at first. Another instance of 

 movement with the same object, which may be explained in a 

 similar manner, is that of the seed-vessel of the common Squirt- 

 ing- Cucumber (Momordica Elaterium). This, when ripe, very 

 readily separates from its stalk ; and its pulpy contents are 

 violently forced out from the aperture thus left. The pulpy 

 matter surrounding the seeds occupies the centre of the fruit, 

 and, by its own increase in amount, distends the cavity ; the 



