THE FLOWER OF THE HIGHER SEED-PLANTS 157 



a diagram for the cross-section of the flower of the white 

 water-lily, of which a partial view of one side is shown in 

 Fig. 115. 



Construct diagrams of the longitudinal section and the transverse 

 section of several large flowers, following the method' indicated in 

 Figs. 114 and 116, but making the longitudinal section show the 

 interior of the ovary.i 



. It is found convenient in dia- 



grams of cross-sections to distin- 

 guish the sepals from the petals 



I II III 



Fig. 116. Diagram of Cross-Sections of Flowers. 



I, columbine ; II, Heatli family ; III, Iris family. In each diagram the dot 

 alongside the main portion indicates a cross-section of the stem of the 

 plant. In II every other stamen is more lightly shaded, because some 

 plants of the Heath family have five and some ten stamens. 



by representing the former with midribs. The diagram- 

 matic 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 



1 Among the many excellent early flowers for this purpose may be men- 

 tioned trillinm, bloodroot, dogtooth violet, marsh marigold, buttercup, tulip 

 tree, horse-chestnut, Jeffersonia, May-apple, cherry, apple, tulip, daffodil, 

 primrose, wild ginger, cranesbill, locust, bluebell. 



