92 VEGETABLE ORGANOGRAPHY. 



verticils of leaves. Thus, the petals of flowers which 

 are regular, and the parts of which are equal in number, 

 arise usually between the sepals, the stamens between 

 the petals, and the carpels between the stamens. But 

 there are some exceptions to this rule : thus, we find 

 the petals opposite the sepals in the Barberry ; the 

 stamens opposite the petals in the Primulaceae, Myr- 

 sineee, &c. As to the real position of the carpels, 

 it has been much less studied than that of the other 

 organs, and without doubt it would give some interesting 1 

 characters in certain families ; but the frequency of 

 their abortion renders their observation delicate. Some 

 examples recently observed, make me think that in 

 perfectly regular plants, where the number of parts is 

 equal in all the verticils, the carpels are always alternate 

 with the sepals, whatever may be the position of the 

 verticil nearest to them : thus, the carpels of the Cras- 

 sulaceas are alternate with the sepals, both in the genera 

 Crassula, Roche a, &c. which have the stamens alternate 

 with the petals, and in Sedum, Cotyledon, Sempervivum, 

 &c. which have the stamens double the number of the 

 petals; the one set alternate, the other opposite them. 



The different dispositions of the parts of the flower 

 may be modified by the number of rows of each verticil, 

 or by the abortion of parts, or because, in several cases, 

 there is developed a cluster of organs resembling that 

 where there is usually found but one : thus, for ex- 

 ample, in several Homalineas we find a tuft of stamens 

 situated in the angle of two contiguous sepals. The 

 same thing takes place in the Myrtaceae, in a very 

 singular manner : thus, the bundle of stamens formed 

 by the union of several, are opposite the petals in 

 Melaleuca, and alternate with them in Astartea. Several 

 double flowers present a fasciculated development, which 

 deserves to be noticed : thus, it is not rare to find 



