206 



FOUNDATIONS OF BOTANY 



Construct diagrams of the longitudinal section and the 

 transverse section of several large flowers, following the 

 method indicated in Figs. 155 and 157, but making 

 the longitudinal section show 



the interior of the ovary. 1 It 

 is found convenient to distin- 



I II III 



FIG. 157. Diagram of Cross-Sections of Flowers. 



I, columbine ; II, heath family ; III, iris family. In each diagram the dot along- 

 side 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. 



guish 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. 157, III) the three dots inside the flower 

 indicate the position of a second circle of stamens, found 

 in most flowers of monocotyledons but not found in this 

 family. 



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

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

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

 daffodil, primrose, wild ginger, cranesbill, locust, bluebell. 



