iT^2o Rural School Leaflet 



In a cyme and a raceme the pedicels on which the flowers are borne 

 are shorter than the main axis, and the flowers are arranged in a sort of 

 pyramid. A form of inflorescence exists, however, in which the flower 

 cluster is flat-topped, as in the common yarrow. This form of inflores- 

 cence is called a corymb. A corymb may be a determinate or an indeter- 

 minate form of inflorescence, in the general use of the term. Figure 9 

 shows a determinate corymb. 



In the forms previously described, the flowers have arisen from diflcrent 

 points on the same or different axes. A form is found rather commonly, 

 however, in which all the flower axes arise from the same point. Such 

 an inflorescence is called an umbel (Fig. 12). 



Various modifications of the forms given exist. A raceme, a cyme, 

 a corymb, or an umbel may be compound ; that is, the axiUary branches of 

 an inflorescence may in turn be divided into the given type. A compound 

 raceme of a loose, irregular nature is called a panicle. 



Leaves are simple or compound. A simple leaf has but one blade. 

 A compound leaf has more than one blade. The various types of leaves 

 are illustrated on page 13 18. There are other types, but most of the com- 

 mon forms are shown. Compound leaves are of two types, pinnately 

 compound and palmately compound (Figs. 10 and 11). A pinnately com- 

 pound leaf has the leaflets arranged along the main axis, arising from dif- 

 ferent points. A palmately compound leaf has the leaflets arising from 

 the same point. If this is learned well, it will be easy to remember the 

 different types of leaf venation. These are discussed later in the next 

 paragraph. Leaves are considered as compound if the leaflets are distinct. 

 If there seems to be a tendency toward division into leaflets, the leaves 

 are said to be lobed. Here, again, there are two types, pinnately lobed 

 and palmately lobed. A good example of a pinnately lobed leaf is the dan- 

 delion; of a palmately lobed leaf, the common sugar maple. The shapes 

 of different leaves can best be shown by the diagrams. The commoner 

 types of margins also are shown. 



Leaf venation is interesting and important. The simplest type is the 

 parallel-veined type (Fig. 14). Here the veins start at one end and extend 

 along beside one another to the opposite etid of the leaf. In case the veins 

 start together and extend in the same direction but do not come together 

 again, as in figure iq, the term palmately veined is used. In a large number 

 of leaves, however, there is one main vein called the midrib from which 

 smaller veins branch (Fig. 17) in which case the tenn pinnately veined 

 is used. Pinnately veined leaves and palmately veined leaves usually 

 have many smaller veins branching in all directions from, the larger veins 

 and giving rise to the term netted-veined. 



