282 Mr. J. Miers on the Nature and Origin 



raphe is visible, extending from the hilar point of the placentary 

 attachment along one side of this sac to the opposite extremity : 

 the only point of organic connexion between the testa and this 

 sac is at the latter termination, where the vessels of the raphe 

 penetrate the shell, to reach the chalaza of the inner integu- 

 ment. Will the advocates of Dr. Gray's hypothesis contend that 

 this free outer membrane and the osseous shell are of identical 

 origin, both resulting from the growth of one ovular tunic? 

 Will it be denied that this free membrane is a production of the 

 original placentary sheath, drawn away from the placenta with 

 its nourishing vessels, and subsequently extended over the whole 

 surface of the ovule ? 



Perhaps the most telhng evidence in support of the view I 

 have here endeavoured to maintain on the one hand, and against 

 the opinion supported by Dr. Gray, on the other, is to be found 

 in the case of Euonymus. Complete details of the gradual and 

 progressive growth of the outer fleshy coating of its seed are 

 recorded by Dutrochet*, who shows that it is not formed till 

 after the impregnation of the ovule; that it first appears as 

 a thickening about the hilum; it then becomes cupuliform, 

 gradually extending itself over the ovular integuments, and 

 finally is seen to envelope the whole seed. One of the most 

 important features observed in the growth there described and 

 figured, is that the vessels of the raphe are enclosed in the soft 

 fleshy tissue of this extraneous coating : this coating has gene- 

 rally been regarded by botanists as an arillus, because of the in- 

 dubitable fact of its subsequent independent growth, and because 

 it is sometimes incomplete or open at one extremity, — a condi- 

 tion I have shown to be an insufficient element in constituting 

 the true character of an arillus f. Dr. Asa Gray has, however, 

 described and figured these same facts J, showing first the ana- 

 tropal ovule of Euonymus, in fig. 6, with the lateral raphe in its 

 placentary sheath agglutinated to the primine ; figs. 7 & 8 exhibit 

 the progressive increment of this fleshy coating over the primine, 

 and fig. 10 its completion as an entire " pulpy red arillus.^' 

 Now, according to this, his own evidence, if the raphe be at first 

 agglutinated to the primine in the ovule, and it be afterwards 

 found imbedded in this " pulpy arillus,^' which he acknowledges 

 and figures as of extraneous growth, proceeding from the 

 hilar point of its placentary attachment, how can the vessels of 

 the raphe have left their first-shown position in the ovule, and 

 subsequently have found their way into the tissue of the arilli- 

 form tunic ? How can so manifest a development be explained 



* Mem. (lu Mus. viii. 270. tab. 1. fig. 30. 



t Linn. Trans, xxii. 83. 



X Gen. Unit. States, ii. 18/. pi. 171. 



