374 ON CHORISIS. 



circle to an indefinite number, the increase being chiefly in the inner 

 ones. Whenever a flower presents a crowd of similar organs, whether 

 manifestly in successive circles, or by their closeness thrown into a con- 

 fused mass, the explanation which first occurs to the botanist is multi- 

 plication of the circles, whether there may be sometimes reasons for, 

 rejecting this and seeking another may be afterwards considered. 



3. Our third principle relates to the position of the circles. The' 

 most natural and general is with the parts of each (the numbers con- 

 forming) alternate with those of the circles without and within it. This. 

 evidently depends on the same spiral plan of growth which produces 

 the arrangement of leaves on a stem, the members of the successive 

 circles being indeed produced in the same plane, but when some growth 

 becomes necessary to obtain space for another circle, the advance of 

 the axis being as usual spiral, and to a degree just sufficient to make 

 the parts alternate, but besides that a whole circle may be so nearly sup- 

 pressed by close pressure, as to be scarcely, if at all, perceptible, which 

 would make those immediately within and without appear opposite, 

 the alternation being maintained by the unnoticed intermediate circle^, 

 which is doubtless the true explanation of the stamens opposite to the 

 petals in the Primrose family , it is quite conceivable that in certain 

 cases the spiral course might be either prevented, or carried too far for 

 alternation, the parts thus becoming opposite and abnormal examples, 

 occurring in which this is seen to take place, proves that we are justi- 

 fied in assuming it as a sufficient explanation of the rare instances in 

 which adjoining circles with opposite parts occur. Dr Lindley has- 

 justly appealed to varieties of Camellia, in which the petals are ranged 

 in regular lines, giving the flower a star-like aspect as proof of the- 

 possibility of the opposite arrangement taking the place of the alter- 

 nate, and those who think otherwise are driven to tlie most extrava- 

 gant suppositions to evade the force of his argument. But I must af- 

 terwards recur to this subject in another connection. At present I 

 wish to show the real nature of the law of alternation, and the possi- 

 bility of deviation from it in exceptional cases, without disturbing our 

 idea of the plan of structure or driving us to imagine other causes in 

 operation. 



4. The degree and mode of development of the separate leafy organs 

 which form each circle may vary from the smallest to the fullest ex- 

 tent, and through several remarkable differences of form. All thfr 

 parts of the flower consist of leaves modified in their devolpment, and 



