86 Mr. Brown's Observations on the 



the corolla of Composita;, one peculiarity actually existing is 

 lost*. 



The principal peculiarity, however, consists in the corolla of a 

 syngenesious plant, when reduced to its smallestnumbcr of nerves, 

 having these nerves alternating with its segments in the tube. I 

 am acquainted with no instance of this order of reduction in th-e 

 nerves of any other nionopetalous corolla, but I observe an ap- 

 parent tendency to it in Portlandia and Catesbcea, In the tube 

 of the corolla of both these genera there are ten nerves, of which 

 the five that alternate with the segments are manifestly stronger, 

 and seem to furnish the greater part of the vascular system of the 

 upper part of the tube and of the segments ; the intermediate 

 nerves being there somewhat like recurrent branches. 



I shall conclude this subject by observing, that although the ex- 

 istence of nerves alternating with the segments of a nionopetalous 

 corolla, dividing below the sinus and uniting their branches at the 

 apex of the segment, be rare, this disposition is comparatively fre- 

 quent in a monophyllous calyx, especially where its aestivation is 

 valvular. Labiatae furnish the most striking examples of this 

 structure. I am not however acquainted with any instance of a 

 calyx having five nerves only, and those alternating with its seg- 

 ments- 



Tiie (estivation or condition of the corolla before expansion is 

 the subject of my second remark on Compositse. I have, in the 



* A still stronger objection to M. Cassini's definition is, that while its application to 

 Compositae is only hypothetical, it very nearly corresponds with the actual disposition of 

 vessels in certain polypetalous genera. Thus in Pittosporum revoluticm, each of the petals 

 has three nerves with distinct origins. Of these the two lateral, evidently within the 

 margins, less so, however, than in Hymenopappus, are quite simple in the ungues, and 

 ramify more or less in the laminae, near the top of which they unite with each other and 

 with the middle nerve. 



observations 



