REPRODUCTION. Oii) 



and to each other, is what constitutes a tree. What 

 are called knots in wood are the result of germs, 

 M^hich, in consequence of the accumulation of 

 nourishment around them, are developed to a cer- 

 tain 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 develope- 

 ment of germs from the edges of the leaves, and 

 the subsequent separation of the new plant thus 

 formed. In this respect the process is analogous to 

 the natural mode of multiplication met with in the 

 lower orders of Zoophytes, such as the Hydra. At 

 the earliest period at which the young of this ani- 

 mal is visible, it appears like a small tubercle, or 

 bud, rising from the surface of the parent hydra: 

 it grows in this situation, and remains attached for 

 a considerable period ; at first deriving its nourish- 

 ment, as well as its mechanical support, from the 

 parent ; then occasionally stretching forth its tenta- 

 cula, and learning the art of catching and of swal- 

 lowing its natural prey. The tube, which constitutes 

 its stomach, at first communicates by a distinct 

 opening with that of its parent: but this opening 

 afterwards closes; and the filaments by which it is 

 connected with the parent, becoming more and more 

 slender, at length break, and the detached hydra 

 immediately moves away, and commences its career 



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 circumstances are favourable. These 

 portions are called eyes ; and each of them, when planted separately, 

 are readily evolved, and give rise to an individual plant. 



VOL. II. M M 



