282 TBEES; THE IB FOBMS AND [Feb., 



wonderful phenomenon called growth. Of physical laws we know 

 something, but life is a physiological constant that seems to defy 

 knowledge. 



The first of the two types of tree described may be called social, 

 because it results from conditions that exist only in the presence of 

 contiguous trees. The second may be called solitary, because it 

 Jesuits from conditions that exist only in the absence of contiguous 

 trees. The first type is characteristic of a tree much in demand by 

 the timber merchant; the second is characteristic of a tree much 

 esteemed for public parks, avenues, parks around private mansions, 

 and wherever a beautiful tree is possible and desirable. Both types 

 begin life under similar conditions. A tree of either type springs 

 from a solitary seed ; it is not till after germination that the plant is 

 subjected to those conditions that determine its typical character. 

 To understand, therefore, how an acorn germinates is to understand 

 how an Oak tree of either type begins life. Not only so, but to under- 

 stand how any single seed with two cotyledons, or seedleaves, 

 germinates, is to undei^gtand in a general way how all dicotyledo- 

 nous plants germinate. Let us take a seed of the common garden Bean, 

 The conditions necessary to germinate that Bean are said to be moisture, 

 heat, oxygen, and darkness. We may reduce these to two, namely, heat 

 and moisture. Darkness is by no means an essential condition, and 

 the amount of oxygen necessary will be forthcoming in the water. 

 Take a glass vessel — a toddy glass will do ; fill it with water and 

 place the Bean in it. Keep the glass in a room where it may be 

 frequently seen, and keep the temperature of the room about 

 summer heat. By observing what takes place within the glass 

 we shall discover first a sensible enlargement of the seed. If we 

 are careful, especially if we are sufficiently sceptical as to things 

 being what they appear to be, we shall have placed more seeds than 

 one into the glass, so that we may extract one of them and so assure 

 ourselves that the enlargement is due to absorption of the water in 

 the glass. The next thing we shall observe will be the radicle, or 

 root of the young plant, protruding at a point near one end of the seed. 

 We may doubt its being the radicle, but by-and-by our doubts will be 

 removed by the appearing of the plumule, or ascending portion, at the 

 opposite end of the seed on the same side. By an internal law of 

 growth, which we cannot explain, the plumule ascends and the radicle 

 descends. The plumule has been called the ascending axis, and 

 the radicle the descending axis. We shall see, however, that 

 one axis is all that is present, and that from a point in 

 it, growth takes opposite directions. At this point we shall also 

 observe that the axis is attached laterally to the two lobes of the 

 seed — the cotyledons in this case. On the radicle we shall discover 



