692 SCIENTIFIC RECREATIONS. 



are washed on to the reef, die, decay, and leave behind a thin layer of 

 mould, which process being repeated again and again, forms an elevated 

 edge to the reef, enclosing a lake, or " lagoon " as it is called, the waters of 

 which evaporate, and the space is filled up in the same way as the edge was 

 formed, together with the excrements of birds, etc., forming layer after layer 

 of mould, and the surface becomes fit for the growth of larger seeds, as the 

 cocoa-nut, banana, etc., which are drifted on to it by the waves ; in this way 

 a coral reef becomes an island fit to be inhabited by man and other animals. 

 It is impossible for any person not accustomed to observe the manner 

 of the propagation of the fungi, to understand a written description, for the 

 fructification of these plants are very varied in the manner of the develop- 

 ment of the spores. They are not generally hurtful, but much caution 

 should be observed in the matter of the mushroom, which may be distin- 

 guished by the pale pink and black of the under part. There are many 

 poisonous fungi, but the greater number are harmless, though they are not 

 intended for food. They simply clear away the decaying growths, and act 

 as safety-valves to Nature by carrying 'away what is not required, to give it 

 to the air again to be renewed into life. 



The vegetable kingdom forms the link between the minerals and the 

 animals. The vegetable derives food and nourishment from water, carbonic 

 acid, and ammonia, which are, as we already know, made up of certain 

 elements, and thus supply us all with food. They give out oxygen for the 

 use of animals, and are thus, in another sense, the source of life. The 

 growth of a plant is very interesting, and we may conclude by following it. 

 The seed is sown, and the cells of the " cellular tissue " become 

 developed, passing some upwards, some downwards, to form a radicle or 

 plumule, as explained. The latter carries up the cotyledon, which begins to 

 decompose carbonic acid from the atmosphere, and fixing the carbon as 

 woody fibre. The leaves are then formed and more fibres, and so on for every 

 leaf; thus the number of woody fibres which form the trunk of a tree 

 is in proportion to the number of leaves which that tree has borne, from 

 which we come to the conclusion that the size of the trunk of a tree is the 

 sum of all its branches. While all this is going on, the cellular tissue of the 

 downward part or radicle also becomes developed and divides out into roots, 

 on the surface and at the extremities of which are minute cellular bodies 

 called " spongioles " (from their power of absorbing moisture), which take up 

 the fluid of the earth which surrounds them ; this moisture ascends through 

 the vessels of the plant till it arrives at the surface of the leaves, where it is 

 exposed to the action of light and sunshine. The ascent of the moisture of 

 the earth was first correctly explained by Du Trochet, and is owing to a 

 peculiar power which he discovered, and which is called " Endosmose " ; this 

 consists in the tendency which a fluid has to penetrate a membrane on the 

 other side of which is a fluid of greater density than itself. This may be 

 seen by the following experiment : obtain a piece of glass tubing about a 

 foot long, having the end blown out into the form of a bell, as in fig. 825, tie 



