22 Mr. J. Miers on the Development 



radicle, and comes away from the chalaza without discoloration, 

 as easily as from all other parts of the surface ; in fact, notwith- 

 standing its attenuation, it presents all the characters of albumen. 

 Intermediate between this and the external integument is a deli- 

 cate membrane, which is separable with some difficulty, this being 

 the tegmen, finely reticulated : the external testa is much thicker, 

 opake, with a rugose surface. Upon raising the tegmen, we 

 find, lying beneath it, several bundles of spiral threads in ana- 

 stomosing bands, so loose that each fibre can be easily drawn 

 out separately ; these bundles of vessels constitute the branching 

 raphe just described, the i*amifications of which appear to issue 

 from the chalaza, where the integuments are united in a solid 

 disk. The source whence these vessels derive their origin in the 

 chalaza may, however, be traced to the main cord of the raphe, 

 which forms a thick bundle running from the hilum to the basal 

 disk. The two integuments are so closely agglutinated together, 

 that it is not easy to determine through which of them the 

 branching portions penetrate ; the main cord is manifestly in 

 the outer tunic. 



On two former occasions, I recorded two very unusual cases 

 in which the raphe becomes entirely peripherical, that is to 

 say, first runs in the usual manner up one side from the 

 hilum to the chalaza, and then returns again along the oppo- 

 site side of the seed to the hilum — in both directions in the form 

 of a simple continuous cord : the one instance was in Stemo- 

 nurus*, a genus of the Icacinacece ; the other appeared in Cucur- 

 bitaceaf. I have yet to show that a similar abnormal course of 

 the raphe is universal, as far as I have been able to ascertain, 

 in Rhamnacea. The consideration of this peculiar development 

 will be deferred till I have detailed all the curious circumstances 

 connected with it, in a memoir just completed. 



In the Euphorbiacece, the raphe, as a thick simple cord, runs 

 in a straight line from the hilum to the opposite chalazal extre- 

 mity, where it is imbedded in the outer tunic, which is some- 

 times as thick and fleshy as in Magnolia, and where, as in that 

 genus, a distinct bony shell intervenes between that coating and 

 the thin inner integument : this raphe perforates the shell 

 through a small diapylar foramen, to reach a small chalaza at 

 the base of that integument; and out of this chalaza I have 

 sometimes observed other vessels distributed over the area of the 

 tegmen, in ten or fewer radiating and almost parallel bands 

 which extend from the base to the apex. The existence of an 

 external arilline, in which the main cord of the raphe is im- 



* Ann. Nat. Hist. 2ser. x. 33 ; Contributions to Botany, i. p. 83, pi. 13 ; 

 Trans. Linn. Soc. xxii. p. 98, pi. 19. figs. 6, 7, 8, 9. 

 t Trans. Linn. Soc. xxii. p. 92, pi. 19. figs. 47, 48, 49. 



