544 CONSERVATIVE ORGANS. [LECT. X. 



papilla, while another enters the surrounding cel- 

 lular matter. This point is the germ of the new 

 plant ; and the vessel, or rather fascicle of vessels, 

 entering the cellular matter is its umbilical cord. 

 As soon, therefore, as circumstances favourable to 

 its evolution are present, the same vital actions 

 commence in it to promote its growth, and for the 

 formation of new parts, as occur in gems situated 

 on tubers; the leaf, like the tuber, supplying 

 the necessary nutriment, until the roots of the 

 young plants are capable of taking up the nu- 

 tritious fluids of the soil; after which it decays, 

 its assistance being no longer required. In 

 tracing the progress of the germ, we perceive 

 that the radicles shoot out from the surface of the 

 rough papilla ; while the two first leaves of the 

 young plant, imperfectly developed and applied 

 face to face, push out from the edge of the ser- 

 rature on the same plane as that of the surface of 

 the leaf; but the young plant afterwards turns up- 

 wards, so as to rise and stand erect on that surface. 

 These two primordial leaves are always developed, 

 and sometimes expanded, before the radicles make 

 their appearance. But the real proliferous leaf, 

 such as that of Cotyledon calycinum, must not 

 be confounded with leaves which became pro- 

 liferous only when separated from the tree and 

 planted in the ground, under favourable circum- 

 stances; as, for example, those of the Lemon tree ; 



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