408 PROPAGATION OF THE SPECIES. CHAP. IX. 



one or more cortical scales, which defend the tender 

 gem and are attached to it only by the base. In 

 buds it is deciduous, in bulbs it is permanent : but 

 it does not form a complete envelope, being always 

 open at that part where the gem is to burst out ; or if 

 shut, it is shut only by the over-lapping of its parts. 

 Fourth Lastly, the gem is distinguished from the seed in 



BftJUTICfl 



its mode of developement. The integuments of the 

 seed perish after germination, but the covering or 

 appendages of the gem do not. They are incor- 

 porated into the substance of the new plant, as in 

 the Propago and Gongylus ; or at least they con- 

 tinue to vegetate along with it, as in the case of the 

 i scales of the bulb. The gem sends out a number of 

 small roots formed from the bark, and but seldom 

 one ; while the seed sends out one main root only 

 from the pre-existing radicle, and but seldom more 

 than one. In the gem, the interior part is first 

 formed and then the appendages or covering ; in 

 the seed the integuments are first formed, and then 

 the embryo appears. 



Definition If the scope of the above distinctions is taken into 

 "' the account the definition of the gem will then be 

 as follows : The gem is an organized substance 

 bursting from the surface of the plant without the 

 aid of sexual apparatus, or previous fecundation ; 

 and developing its parts either by forming a con- 

 tinued extension of the parent plant, or by detaching 

 itself from the parent plant altogether, and forming 

 a new individual. 



