LKSSON 8.] TIIKIK FOUMS AS TO GENKUAL OUTLINK. 57 



moil Pickerel-weed of our ponds, in the Banana (Fig- -17), and many 

 similar plants of warm climates. 



1-45. Netted- veined leaves are also of two sorts, as is shown in 

 the examples already referred to. lu one cjise the veins all ris9 

 from a single rib (the midrib), as in Fig. 83. Such leaves are called 

 fealher-veined or pinnately-veined ; both terms meaning the same 

 thing, namely, that the veins are arranged on the sides of the rib 

 like the plume of a feather on each side of the shaft. 



146. In the other case (as in the Button wood, Fig. 50, Maple, 

 &c.), the veins branch off from three, five, seven, or nine ribs, which 

 spread from the top of the leaf-stalk, and run through the blade like 

 the toes of a web-footed bird. Hence these are said to hQ pahnatcly 

 or digitately veined, or (since the ribs diverge like ra}s from a 

 centre) radiate-veined. 



147. Since the general outline of leaves accords with the frame- 

 work or skeleton, it is plain that feather-veined leaves will incline to 

 elongated shapes, or at lejist will be longer than broad ; while in 

 radiate-veined leaves more rounded forms are to be expected. A 

 glance at the following figures shows this. Whether Ave consider 

 the veins of the leaf to be adapted to the shape of the blade, or the 

 green pulp to be moulded to the framework, is not very material. 

 Either way, the outline of each leaf corresponds with the mode of 

 spreading, the extent, and the relative length of the veins. Thus, in 

 oblong or elliptical leaves of the feather-veined sort (Fig. 87, 88), 

 the principal veins are nearly equal in length ; while in ovate and 

 heart-sliaped leaves (Fig. 89, 90), those below the middle are 

 longest; and in leaves which Aviden upwards (Fig. 91-94), the 

 veins above the middle are longer than the others. 



148. Let us pass on, without particular reference to the kind of 

 veining, to enumerate the principal 



149. Furms of Leaves as to Geiirral Outline. It is necessary to give 



names to the i)rinci[)al shapes, and to define them rather precisely, 

 since they afford the easiest marks for distinguishing species. The 

 same terms are used for all otlier fiattened parts as well, such as the 

 petals of the flowers ; so that they make up a great part of the 

 descriptive language of Botany. We do not mention the names of 

 common plants which exhibit these various shapes. It will be a good 

 exercise for young students to look them uj) and apply them. 



150. Begimiing with the narrower and proceeding to the broadest 

 forms, a leaf" is said to be 



S & F— 4 



