THE LEAVES OF VASCULAR PLANTS. 257 



of development which is visible to our eyes ; it is thus 

 that in penninerved leaves the limb is entire, if the 

 lateral parenchyma of all the lateral nerves remains 

 united as far as the top of these nerves ; but if the 

 nerves are too distant from each other in proportion 

 to the possible development of the parenchyma, then 

 the portions formed by the development of the secon- 

 dary nerves, or the Lobes, as they are called, in a 

 general manner, remain united, — for example, about 

 half way ; the projecting parts take the name of 

 Divisions, and the sinuses that of Fissures ; and to 

 express at the same time that the leaf has pinnate 

 nerves, and that its lateral lobes are united about half 

 way, it is said to be Pinnatifid. 



Let us suppose either a greater separation of the 

 secondary nerves, or a parenchyma less disposed to be 

 developed, the lobes may be only united at their base ; 

 they are then called Partitions, and the leaf is said to 

 be Pinnatipartite ; lastly, the nerves may be still 

 more separated, or the parenchyma still less developed, 

 the lobes will be totally independent and not united 

 together ; then they take the name of Segments, and 

 the leaf is said to be Pinnatisected. It sometimes 

 happens that, at the base of the petiole, the lobes are 

 completely isolated, and more or less united above; 

 this inequality is expressed by saying that the leaf is 

 Lyrate : if one wishes to say that a penninerved leaf 

 has its lateral nerves separate, except at the apex, 

 '.vithout expressing where the junction is, the leaf is 

 said to be Pinnatilobed. 



We easily understand that all that I have said of 

 the secondary nerves may be said of the tertiary, or, in 

 other terms, each of the projecting lobes may be pin- 

 natifid, pinnatipartite, or pinnatisected : this is ex- 

 pressed by saying Bipinnatifid, &c. ; the lobules 



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