128 BOTANY OF CONGO. 



According to Mr. Lockhart a frutescent species of 

 «5] Euphorbia, about eight feet in height, with cylindrical 

 stem and branches, was observed, planted on the graves of 

 the natives near several of the villages ; but of this, which 

 may be what Captain Tuclcey has called Cactus quadran- 

 gularis in his Narrative (p. 115), there is no specimen in 

 the herbarium. 



COMPOSITE. It is unnecessary here to enter into 

 the question whether this family of plants, of which 

 upwards of 3000 species are already known, ought to be 

 considered as a class or as an order merely ; the expediency 

 of subdividing it, and affixing proper names to the divi- 

 sions, being generally admitted. The divisions or tribes 

 proposed by M. Cassini, in his valuable dissertations on 

 this family, appear to be the most natural, though as yet 

 they have not been very satisfactorily defined. 



The number of Compositje in the collection is only 

 twenty-four, more than half of which are referable to 

 Helianthea and Vernoniacea of M. Cassini. The greater 

 part of these are unpublished species, and among them are 

 five new genera. The published species belong to other 

 divisions, and are chiefly Indian : but one of them, Agera- 

 tum conyzoides, is common to America and India ; the 

 Struchium, (or Sparganophorus) of the collection does not 

 appear to me different from that of the West Indies ; and 

 Mikania chenopodifolia, a plant very general on this line of 

 coast, though perhaps confined to it, belongs to a genus of 

 which all the other species are found only in America. 



Baron Humboldt has stated^ that Compositse form one 

 sixth of the Phsenogamous plants within the tropics, and 

 that their proportion gradually decreases in the higher 

 latitudes until in the frigid zones it is reduced to one 

 thirteenth. But in the herbarium from Congo Compositse 

 form only one twenty-third, and both in Smeathman's col- 

 lection from Sierra Leone and in Dr. Roxburgh's Flora 

 Indica, a still smaller part, of the Phsenogamous plants. 

 In the northern part of New Holland they form about one 



' In op. citat. 



