45« 



SCIENTIFIC NEWS. 



[Nov. 2, 1888, 



when it has been made, this takes place in various 

 parts of the plant. The cell where starch has been pro- 

 duced may itself serve as a reservoir, but usually the 

 newly formed material is transferred to other growing 

 parts, such as the buds and the root. In the case of the 

 pea-plant much material is consumed, first in growth, 

 and later in making the substance of the pea-seeds in 

 the fruit. In many cases the newly formed material is 

 transferred to some thickened part of the plant under- 

 ground, some part of the stem or root, where it is kept 

 safe till the plant begins to form its seeds. When re- 

 serves of material are thus formed underground they 

 are less liable to be attacked by animals. The young 

 pea-plant is destroyed if a pigeon eats off the top of the 

 plant ; a potato plant may have its leaves cropped by a 

 cow and yet survive, because it has a reserve of starch 

 in its tubers or thickened underground stems. 



Now, as to the storage of force in plants, this is always 

 the result of growth, and examples are mostly seen in 

 the flowers and fruits. The flowers and fruits of plants 

 may be said to be the results of their highest stages of 

 development ; a long series of actions takes place in the 

 plant before it produces flowers and fruit. Many acts of 

 growth and much formation of new material occur in 

 the plant before the highly complex flowers appear, and 

 it must be remembered that the formation of new 

 material results from the action of light upon structures 

 in the leaves. If the plant be healthy and has accumu- 

 lated reserves of starch, flowers and fruit can form in 

 parts excluded from light — light is not necessary to the 

 formation of flowers. Flowers may grow from flower- 

 buds without the stimulus of light ; it seems as though 

 some intrinsic forces were accumulated in the plant 

 (probably the results of its inheritance) which will suffice 

 for the growth of the flower from the bud if the plant has 

 accumulated sufficient material. 



A good example of storage of force is seen in the 

 Kalmia-blossoms (Kalmia latifolia). The corolla closes 

 in both the style, and the stamens, which are seen 

 just inside the corolla; the upper enlarged part of 

 the stamen is its anther, or pollen-box, and this 

 is lodged in a small pocket of the corolla. The stalk of 

 the stamen, or filament, becomes bent as the corolla 

 opens. The expansion of the corolla curves the filament 

 outwards ; this creates a mechanical tension in the fila- 

 ment. It is said that the "corolla opens;" this is a 

 result of a certain mode of growth in the corolla which 

 it is important to understand. While the corolla is in 

 the bud state the inner surface of the corolla grows less 

 quickl}' than the outside, and as a result the inner sur- 

 face of the corolla remains concave, and the corolla 

 closed. When growth is almost completed the inner 

 surface of the corolla grows more quickly, with the 

 result that what was the inner and concave surface now 

 becomes convex and the flower opens, the style is ex- 

 posed to the pir, its stigma becomes the most prominent 

 part of the flower, and the filaments of the stamens are 

 placed under tension, their upper surfaces becoming 

 convex ; the anthers aro still held mechanically in the 

 pockets of the corolla. It may be seen that the cause 

 of the tension in the filaments results from the movement 

 of the parts of the corolla, and that this results from an 

 alteration in the ratio of growth of the surfaces of the 

 corolla. The tension in the filaments results from 

 the ratios of growth in the surfaces of the corolla, 

 and this is due to the inherited intrinsic forces in 

 the plant. The anther, or pollen-box, discharges 



pollen through a small orifice at the apex of each cell. 

 When an insect settles upon the flower it touches first 

 the stigma, which is the highest part of the flower; the 

 shaking which the flower thus receives liberates some of 

 the stamens, and the anthers being liberated fly upwards 

 and discharge their pollen on to the insect, which flies 

 away with some of the pollen of this flower adherin? to 

 it. Now consider two such flowers and the bee which 

 passes from one to the other collecting honey. The first 

 open flower that he visits dusts his body with pollen ; 

 this he carries to the next flower visited, and there de- 

 posits some upon the stigma, at the same time receiving 

 a fresh supply of pollen, which he carries off to the next 

 flower. Thus cross-fertilization of the flower is effected. 

 Whenever we come to observe movements of parts in 

 plants the case is much more complex than with condi- 

 tions of growth, the results much more striking and won- 

 derful, and such examples are found in the most highly 

 developed parts of the plant. Such examples are not 

 spoken of as due to intelligence in the plant, but are very 

 analogous in their outcome to acts that are termed signs of 

 intelligence in animals. Storage of force is seen in 

 the growth of many fruits, and usually leads to the 

 scattering of the seeds by mechanical means. In a 

 species of wild geranium (Geranium dissectum), when 

 the other parts of the flower have fallen, the central 

 axis elongates in its growth ; each seed is con- 

 tained in a case, which is supported by a rod of tissue, 

 which in the early condition of the flower forms part of 

 the central axis, but gradually becomes detached from it. 

 When the seeds are ripe the case containing the seed 

 becomes detached from the base of the supporting 

 column and splits open, the rod is in a state of tension, 

 and eventually becoming detached with a jerk, the seed 

 is thrown some little distance. The cause of the tension 

 in the rod is the unequal growth which occurs in its inner 

 and outer surfaces ; the inner surface, or that next to the 

 central support, grows the most ; tension or storage of 

 force is thus produced, the mechanical energy is sud- 

 denly displayed when any jar is communicated to the 

 plant, and scattering of the seed results. Examples oi 

 the storage of mechanical force might be multiplied. 

 The lessons we may learn are that conditions of growth 

 may produce mechanical action, which for a timemsybe 

 stored up in latent form, and then become suddenly 

 manifested in movement, producing a visible effect, whicn 

 in its turn leads to important results to the species. 

 Cross-fertilization is very important in producing good 

 seeds. Scattering of the seed is essential to the spread 

 of the species over the surface of the earth. 



— »->t?»^<f- > — 



A Petrified Forest. — M. Philippe Thomas announces 

 to the Paris Academy of Sciences, that he has dis- 

 covered in Tunisia a gigantic forest, all the trees of 

 which are silicified, and which is thus an exact copy 01 

 the celebrated forest of agate at Cairo. M. Flische has 

 recognised the same species as in Egypt, such as Arau- 

 carioxylon egyptiacum, Bambusitcs Tlioniasi ) and Cossoni, 

 a Ficoxylon, an Acacioxylon, etc. But whilst the 

 palaeontologists, Hooker, Fraas, Zittel, and others, dis- 

 puted on the age of the forest at Cairo, which seemed 

 cretaceous to some and quaternary to others, the age of 

 the Tunisian forest is manifest, and is referred to the 

 pliocene or upper tertiary. M. Bleicher attaches the 

 fact of the silicification of trees to the presence of free 

 gelatinous silica in the enclosing rocks. 



