REPRODUCTION. 589 



developed at the axillcB of the leaves ; that is, at 

 the angles of their junction with the stem ; and 

 also at the extremities of the fibres of the stems ; 

 their developement being determined by the 

 accumulation of nourishment around them. 

 They first produce huds, which expanding, and 

 putting forth roots, assume the form of shoots ; 

 and the successive accumulation of shoots, which 

 remain attached to the parent plant,* and to 

 each other, is what constitutes a tree. What 

 are called knots in wood are the result of germs, 

 which, in consequence of the accumulation of 

 nourishment around them, are developed to a 

 certain extent, and then cease to grow. The 

 Lemna, or common Duckweed, which consists 

 of a small circular leaf, floating on the surface 

 of stagnant pools, presents a singular instance 

 of the developement of germs from the edges of 

 the leaves, and the subsequent separation of the 

 new plant thus formed. In this respect the 



* In some rare instances the shoots are removed to a distance 

 from the parent plant, by a natural process : this occurs in some 

 creeping plants, which propagate themselves by the horizontal 

 extension of their branches on the ground, where they dip, and 

 strike out new roots, giving rise to stems independent of the 

 original plant. This also sometimes happens in the case of 

 tuberous roots, as the potatoe, which contain a number of germs, 

 surrounded by nutritive matter, ready to be developed when cir- 

 cumstances are favourable. These portions are called eyes ; 

 and each of them, when planted separately, are readily evolved, 

 and give rise to an individual plant. 



