OF PLANTS CALLED COMPOSITE. 275 



much resembles ; or thirdly, that it is more analogous to m 

 the outer calyx of Scabiosa, which M. Cassini seems to 

 consider different in its nature from both these parts. 



But the order of expansion in Lagasca, which is, though 

 with some degree of irregularity, from centre to circum- 

 ference, or that of the compound capitulum, seems to 

 decide the question respecting the envelope of each flower, 

 and to establish its identity with involucrum : nor does this 

 involucrum differ materially from that of Echinops, except 

 in the reduced number and confluence of its component 

 parts. 



The real structure of Casulia is perhaps less obvious. 



This genus, which was first published by Dr. Roxburgh, 1 

 is referred by him to Polygamia segregata ; the tubular 

 envelope or involucrum of each floret being described as 

 distinct from the included ovarium. 



Kcenig, on the other hand, by whom the genus was dis- 

 covered, and whose account of it is given in the same work, 

 describes the partial involucrum of Roxburgh as the sur- 

 face of the ovarium itself ; its segments being, according to 

 him, a pappus of two leaves. And lastly, Willdenow, 

 regarding this involucrum as merely palea? of the recep- 

 tacle, refers the genus to Polygamia sequalis ; in which 

 order it is continued, both in Persoon's Synopsis, and in 

 the second edition of Mr. Aiton's Hortus Kewensis. 



This last view of the structure seems the most erroneous 

 of any, and was probably adopted by Willdenow, in con- 

 sequence of his having added to the genus a second species 

 not really belonging to it, and which I shall have occasion 

 to notice in another part of my subject. 



An examination of the parts of fructification in different 

 stages reconciles the opposite statements of Kcenig and [95 

 Roxburgh; for I find that at the time of flowering the 

 envelope of each floret is, as Roxburgh has figured it, dis- 

 tinct from the ovarium, with which, however, in a more 

 advanced stage its tube becomes firmly united ; a fact that 

 sufficiently accounts for Kcenig's description. 



1 In Corom. Plants, i, p. 64, t, 93. 



