84 Mr. J. Miers on the Tribe Colletiese, 



the dorsal groove is more shallow, and embraces the other cor- 

 responding portion of the raphe and integument, so that, on 

 detaching the external crust, the raphe comes away with it, 

 tearing itself from the rest of the integument*. 



This structure is repeated, under somewhat varied circum- 

 cumstances, in Rhamnus chlorophorus, Dene. : here, however, the 

 raphe is lateral, not dorsal ; the cotyledons are not involutely 

 inflected, as in the former case, but are simply complicated or 

 folded upon one another, so that their midribs stand opposite 

 one margin of the seed, while all the four edges of the two coty- 

 ledons face the contrary margin, the albumen and integuments 

 partaking of the same complicature. A deep groove is thus 

 formed, reaching to the axis, as in R. catharticus, which here is 

 therefore lateral, instead of dorsal ; the raphe does not lie in the 

 bottom of the deep groove, as in the latter species, but as it 

 leaves the chalaza it runs along the mouth of the groove from 

 top to bottom, as in R. Alaternus, and the middle integument, to 

 which it is attached, here makes a deep plicature which nearly 

 reaches the bottom of the groove ; and throughout the whole 

 length of this plicature it is separated on both sides, by a vacant 

 interval, from the inner integument, thus forming a kind of 

 loose, incomplete partition all down the groove. This inter- 

 mediate tunic is membranaceous, and invests all other parts of 

 the seed; it is enclosed within an external, hard, polished, 

 testaceous covering, similar in texture and appearance to that in 

 R. catharticus, but it is not, as in that species, inflected into the 

 groove : the groove is here rather an open slit, always on the 

 sinister margin (looking from the axis of the fruit), and is sur- 

 rounded by a thick callous rim, which, rising from the basal 

 and hilar point of attachment of the seed, extends upwards to 

 one-third or half its length. This crustaceous coating lies close 

 upon the intermediate integument of the seed over its two broad 

 faces; but at its summit, and all along the other margin (oppo- 

 site to that of the groove), a vacant space intervenes between 

 them. The raphe is imbedded in that intermediate integument 

 in the form of a simple cord, the thicker moiety of which runs 

 along the base of the groove, and is free from it at all points, 

 except at the bottom of the groove, where it adheres to it by 

 means of a crustaceous deposit : it continues its course in a 

 peripherical direction, crossing the apical chalaza beneath the 

 free space mentioned, and runs down along the opposite margin 

 of the seed, till it again reaches the pointed base or micropylar 

 extremity of the inner integument. I have frequently succeeded 

 in detaching the entire raphe with a portion of the integument 



* This structure will also be given in detail in plate 33 c of the ' Con- 

 tributions to Botany.' 



