CH. IV 



THE STUDY OF THE SHOOT 



35 



the apex, and they are connected by smaller cross veins, as in 



the leaf of the Lily of the Valley. The reticulate-veined leaf 



differs from the parallel-veined leaf 



in possessing one or more midribs, 



from which veins are produced 



eventually uniting with one another 



to give the leaf the appearance of 



net-work. The Oak bears such a 



reticulate-veined leaf (Fig. 36). 



If the leaf only possesses one 

 mid-rib, the leaf is said to be uni- 

 costate. When the leaf is divided 

 into a number of divisions, and each 

 lobe possesses a mid-rib, it is said 

 to be multicostate. The leaves of 

 the Oak, Beech, Poppy, and Dan- 

 delion, are unicostate, while the 

 leaves of the Monkshood, Castor- 

 oil plant, and Fig, are multicostate. 



The veins of a leaf give it 



strength ; it depends upon the mode of life of the plant what 

 kind of leaves will be produced. Plants which grow in a very 



FIG. 35. Venation of a leaf. 



FIG. 36. Unicostate leaf of Oak. 



FIG. 37. Multicostate and palmate leaf 

 of the Horse-Chestnut. 



exposed position generally have narrower leaves than those 

 which grow in sheltered places. Water plants with submerged 



D 2 



