FLORAL DIAGRAMS 



131 



organs. Equally important in this way are cross sections, 

 which may be recorded in diagrams like those of Fig. 138. 1 

 In constructing such diagrams it will often be necessary to 

 suppose some of the parts of the flower to be raised or lowered 

 from their true position, so as to bring them into such rela- 



tions that all could be cut by a single 

 section. This would, for instance, be 

 necessary in making a diagram for the 



A B C 



FIG. 138. Diagram of cross sections of flowers 



A, columbine; B, heath family; C, Iris family. In each diagram the dot along- 

 side the main portion indicates a cross section of the stem of the plant. In B 

 every other stamen is more lightly shaded, because some plants of the heath 

 family have five and some ten stamens. After Sachs 



cross section of the flower of the white water lily, of which a 

 partial view of one side is shown in Fig. 137. 



It is found convenient, in diagrams of cross sections, to dis- 

 tinguish the sepals from the petals by representing the former 

 with midribs. The diagrammatic symbol for a stamen stands 

 for a cross section of the anther, and that for the pistil is a 

 section of the ovary. If any part is lacking in the flower (as 

 in the case of flowers which have some antherless filaments), 

 the missing or abortive organ may be indicated by a dot. In 

 the diagram of the Iris family (Fig. 138, C) the three dots 

 inside the flower indicate the position of a second circle of 

 stamens, found in most flowers of monocotyledons but not in 

 this family. 



1 For floral diagrams see Le Maout and Decaisne, Traite General de 

 Botanique, or Eichler, Bluthendiagramme. 



