FLOWERING PLANTS INTRODUCTORY 93 



leaf -blade. The leaf -blade may be unbranched, although its 

 margin is more or less deeply indented, and is then described as 

 simple. In other cases the leaf-blade is branched, and appears 

 to be made up of a number of smaller leaf -blades or leaflets. 

 Such leaves are described as compound. The leaflets are most 

 commonly arranged on either side of a stalk which continues 

 the leaf-stalk (pinnate leaves), but they may diverge from the 

 end of the leaf -stalk like the fingers of a hand (palmate leaves). 



The blade of the leaf or of the separate leaflets is traversed by 

 a branched system of conducting and supporting strands which 

 form the veins of the leaf, and persist as leaf skeletons when the 

 softer parts have rotted away. There is often a central vein or 

 midrib running from the base of the blade to its tip and giving 

 off lateral branches, while the fine network extends in the intervals 

 between these. In other cases no midrib is distinguishable, 

 but numerous parallel veins run in the leaf, connected at intervals 

 by finer veins, and so forming a network in a different way. 

 The stronger veins often project on the lower surface of the 

 leaf, and the whole system serves to support the thin expanded 

 blade. The veins are the ultimate branchings of a system of 

 conducting strands which run continuously from the root to 

 the stem and out into the leaves. It is by means of them that 

 the water taken up by the root is brought to the leaf-blade. 



In the special case of the Buttercup the base of the stem is 

 relatively stout, and bears a number of long-stalked leaves which 

 are closely crowded together at their insertion and thus appear 

 to spring from the level of the ground. Above this the inter- 

 nodes of the stem lengthen, but only small leaves are borne at 

 the nodes. The branches in the axils of these bear the flowers. 

 In the axils of some of the lower leaves, in the case of Ranunculus 

 repens, long creeping branches arise, to the consideration of 

 which we shall return. The stem is cylindrical, green or reddish, 

 and hairy. Each foliage-leaf has a wide sheathing base, but 

 no stipules. The leaf -base becomes more strongly concave on 

 passing towards the leaf-stalk, on reaching which the thin ex- 

 panded margin stops. The long firm leaf-stalk is green, and 

 sparsely covered with hairs. It is strongly convex below, but 

 has a narrow, shallow groove on the upper side, i.e. the side 



