44 



HOW PLANTS GROW. 



IM 



i!i 



iii! 



in jiQtiinpp-loaf : h, the blado ; j), tho footstalk ; ' thp stipules, looking like 



a pair of little blades, one on each side of the stu But many leaves have no 



stipules ; many have no footstalk, and then the blade sits directly on the stem (or is 

 nessHc), as in Fi^. 138. Some leaves even have no blade ; but this is uncommon ; 



for in folia<,'e the blade is the essential part. There- 

 fore, in descrihin^ the shaj>e of leaves, it is always 

 the blado that is meant, unless something is said to 

 the contrary. 



121. Leaves are either siwpir ovcompmuul. They 

 are ninijiff when the blade is all of one piece ; com- 

 pdinid, when of more than one piece or blade. Fig. 

 128 to 132, and 133, are examples of compound 

 fj leaves, tho latter very compound, having as many as 

 eighty-one litth^ blades. 



122. Their Structure and Veining. Leaves are com- 

 posed of the same two kinds of material as stems( 1 10), 

 namely, of wood or iibre, and of cellular tissue. The 

 woody or filn'ous part makes a framework of ribs 

 and veins, which gives the leaf more strength and 

 toughness than it would otherwise have, The cellu- 

 lar tissue forms the (/ree?i jmlp of the leaf. Tliis is 

 spread, as it were, over the framework, both above 



and below, and supported by it ; and the whole is protected by a transparent 



skin, which is tv'-med the Kjiidcrinis. 



123. Ribs. The stouter jiieces or tiinbcM's of tho framework are called Rihs. 

 In the leaf of the Quince (Fig. 82), Pear, Oak (Fig. 1 20), Sec, there is only a single 

 main rib, running directly through tlie middle of the blade from Ijase to point ; this 

 is called the M/i/n'h. But in the Mallow, the Linden (Fig. 83), the Maple 

 (Fig. 84), and many others, there are three, or five, or seven ribs of nearly the 

 same size. The bi\inches of the ribs and the branchlets from them are called 



1 24. Veins and Veinlets. The former is the general name for them ; but the iinest 

 branches are particulai-ly called VnnletH. Straight and parallel veins or fine ribs, 

 like those of Indian Corn, or of any Grass-leaf, or of the Lily of the Valley (Fig. 

 3, 85), are called Nerves. This is not a sensible name, for even if in some degree 

 like the nerves of animals in shape, they are not in the least like them in use. 



