176 Mr. J. Miers on some genera of the Icacinaceae. 



or papillary tubes, here sloping outwards on each side the cord ; 

 c, truncated vessels of the marginal plexus ; d, d, small channels 

 of intercameral communication ; e, grand semilunar or crescentic 

 channel of ditto ; /, septum. 



Fig. /• Diagram of vertical section to show the situation of the interseptal 

 vessels : a, a, interseptal vessels ; h, septum ; c, grand channel of 

 intercameral communication ; c?, part of spicular cord. 



Fig. 8. Enlarged view of first-formed chambers of Operculina Arabica : 

 a, central cell or chamber ; b, b, b, probable forms of last cham- 

 bers in process of development. 



Fig. 9. Diagram of vertical section of Nummulites acuta, Sow. : a, spicular 

 cord ? ; b, truncated vessels of marginal plexus ; c, c, chambers of 

 central plane; d, d, vertical interseptal vessels (the "perforations," 

 &c. of Dr. Carpenter) ; e, e, horizontal interseptal vessels ; /, /, /, 

 chambers on each side the central plane ; g, g, g, vertical tubes. 



XVI. — On some genera of the Icacinacese. By John Miers_, 

 Esq., F.R.S., F.L.S. 



[Continued from p. 119.] 



Emmotum. 



This neglected genus was proposed by Desvaux in 1825 upon 

 a plant from Guiana. By Endlicher it was referred to Leretia 

 of the ' Flora Fluminensis/ with which it neither accords in the 

 appearance of the leaf nor the mode of its inflorescence : Hamil- 

 ton's character as given in his ' Prodromus/ notwithstanding its 

 brevity, is sufficiently well marked to show that it does not differ 

 from Poffopetalum, founded by Mr. Bentham in 1840 ; indeed the 

 Emmotum fagifolium J Desv., corresponds with Pogopetalum acu- 

 tuMj Benth., both from Guiana, so as to leave no doubt of their 

 identity : according therefore to the austere rule of science, the 

 latter name must give way to the former. Mr. Bentham in 

 establishing his genus recorded two species, and has since de- 

 scribed two others, and I have now to add a fifth. All the spe- 

 cies, which are from Guiana and intertropical Brazil, seem to 

 form good-sized trees, with very thick coriaceous leaves of a 

 peculiar appearance ; their inflorescence is in axillary crowded 

 fascicles of rather small flowers, which are distinguished by 

 having petals densely beset on their inner face with long red 

 silky hairs arising from an elevated costal nervure. Their chief 

 peculiarity, however, consists in the unusual structure and sin- 

 gular mode of dehiscence of their anthers, which are formed of 

 two opposite, unilocular, valveless, and separate cells, the pollen 

 being discharged extrorsely through a fissure arising from the 

 secession of the dorsal margin of each boat-shaped cell from the 

 very fleshy connective, features that have hitherto escaped obser- 



