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COLOUR, FORM, AND MOVEMENT. 



The Symmetry of Flowers. 



Let us take easy examples. In flowers the bounding 

 lines are symmetrical. That is to say, there is (nearly) 

 always one line which drawn through the flower divides it 

 into two parts which are counterparts of each other ; one is 

 the mirror image of the other. Commonly in flowers there 

 is more than one such line. In our buttercup there are 

 five. 



Draw a buttercup on the board viewed from above, 

 and pass a straight line across the middle of a petal and 

 along the space between the two petals opposite. You see 

 that this can be done five times always with the same 

 result two and a half petals on one side, and two and 

 a half exactly similar petals on the other. (For sim- 

 plicity's sake we neglect all reference 

 to other parts, stamens, etc. We are 

 dealing with the plan of structure.) 

 Such symmetry as is here illustrated 

 may be termed Eadial Symmetry 

 f i f? P\A? (actinomorphic of botanists), and as 



I &j$ if stated above it is the commonest form 

 I p^\ JT\ jPj of flower symmetry. Examine a few 

 ^\N^ ^/// flowers with regard to their symmetry. 

 Now take another example, this 

 time a Violet flower. Draw a surface 

 view, or, what is perhaps better, a 

 floral diagram (Fig. 5). We see at 

 once that in this case there is one 

 line only which can divide the flower 

 into two counter parts. When such 

 is the case we speak of Bilateral Sym- 

 metry (zygomorphic of botanists). 

 Test this rule upon one or two cases, e.g. Primrose and 

 Wallflower. The former shows radial symmetry. What 

 of the latter ? Draw the floral diagram of the Wallflower 

 (Fig. 6) . This presents an interesting case. A line drawn 

 so as to divide the two groups of long stamens and have 

 a short stamen on each side ( A B in Figure) gives the true 

 line of bilateral symmetry, and np other line gives the 



SPUR.-. 



Fig. 5. Floral Diagram of 

 Violet. The line of bi- 

 lateral symmetry is the 

 line passing across from 

 the spur to the odd 

 sepal at the top of the 

 figure. 



