1818.] M. De Candolle on Double Flowers. 333 



stamens become abortive, and where, in consequence of this 

 circumstance, the corolla, the calyx, and the involucrum, expe- 

 rience a remarkable increase of size, with or without a change 

 of form. This mode of transformation seems to be peculiar to 

 aggregate or compound flowers, such as grow in a corymbus or 

 umbel. The viburnum opulus is an example of this kind of 

 transformation. Compound flowers are transformed in two 

 different modes ; in the most common mode the tubular florets, 

 becoming barren, assume the form of a tongue, which is 

 lengthened out, and hangs down on the outside of the head ; 

 but at other times the florets only increase in size, without 

 changing their form. Compound flowers appear to follow two 

 rules in this respect : 1 . The genera, which have the external 

 florets naturally tongue-shaped, are the only ones which are 

 capable of having the central florets transformed into tongues ; 

 2. When the central flowers are transformed either into tongues 

 or into large tubes, they acquire the colour of the natural tongues 

 of the external florets. This affords the only exception to what 

 is a very general law with respect to the colours of flowers, that 

 yellow flowers may assume all the shades of red and white, but 

 that blue and yellow never change one into the other. 



The two following conclusions may be deduced from the facts 

 that have been stated in this paper : 1 . The form, the dimensions, 

 the number, the direction, and the colour of all the parts of 

 flowers, are extremely varied, while their position remains 

 constant ; from which we may learn, that what is styled the 

 insertion of the organs is the only constant character which 

 determines all their anatomy. 



2. Under the title of monstrosities are included double flowers 

 of very different kinds, which have been all confounded together, 

 but which may be systematically arranged, in a manner analogous 

 to that in which Haiiy arranges crystals. The following classi- 

 fication and nomenclature are proposed. 



Petaloid flowers, flores petaloidei, those which become double, 

 by the simple transformation into petals of a part or the whole of 

 the organs of fructification. 



Multiplied flowers, flores multiplicati, those which double by 

 the multiplication or doubling of parts of the corolla, or of the 

 organs of fructification transformed into petals. 



Transformed flowers, flores permutati, those in which the 

 abortion of one or both of the organs of fructification produces 

 a considerable alteration in the form or the dimensions of the 

 floral integuments. 



These form the three fundamental divisions, or classes, the 

 particular characters of which are deduced from the primitive 

 nature of the transformed organ. Thus in the petaloid and 

 multiplied flowers we may distinguish 13 kinds : calycinary, 

 corollary, staminary, and pistillary flowers, the petals of which 

 are respectively owing to the transformation of the calvx, corolla, 



