APPENDIX II 



Nervation, tie arrangement of the fibre-vascular bundles 

 in the leaves. The method of describing the nervation 

 differs somewhat in the Flowering Plants and Ferns. 



I. Flowering Plants. The nerves or ribs which spring 

 directly from the petiole (or stem in sessile leaves) are 

 termed Primary Nerves. The center one or if there is only 

 one is the Mid-rib. If there are several primary nerves 

 spreading from the base the leaf is palmi-nerved or palmately 

 nerved, 3-nerved, 5-nerved, etc., refer to the number of 

 primary nerves. If a" I the primary nerves are parallel or 

 nearly so, the leaf is parallel-nervedr The larger nerves 

 which spring laterally from the primary nerves are the 

 Secondary Nerves, and those that arise from these the Tertiary 

 Nerves, which may, as well as the_ nervation of a higher order, 

 be also called the nervules. If the nervules are very 

 numerous and anastomose with one another the nervation is 

 reticulate, but this expression is sometimes also nsed merely 

 as the antitheses of parallel-nerved. 



II. Ferns. The continuation of the stipes or stalk of tno 

 frond into the blade is called the rachis, or primary rachis, in 

 a compound or deeply divided frond, rachis or mid-rib, in a 

 less divided or simple frond. The branches Jxpm the primary 

 rachis in a bi-many- pinnate or deeply 2-many-pinnatifid froncl 

 are the secondary rachides, and the branches from these again 

 the tertiary rachides according to the state of division of the 

 frond. The nerves which spring from the mid-rib or rachis 

 of a simple frond or from the secondary or tertiary etc. 

 rachis, as the case may be (depending on the degree of 

 branching in the frond) in a more compound frond are the 

 costa. Those that spring from the costae are the veins, sxA 

 those of a higher order the venules. A costa is hence the 

 mid-rib of a lobe. 



Node, the plane of insertion of a leaf on the axis. 



Nnt, a hard, dry 1 -seeded indehiscent fruit. 



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