82 MR. MIERS ON THE OUTER FLESHY COVERING OF THE SEED 



delicate inner pellicle of the aril will be found attached to it, which has been torn away 

 by the raphe. ^Vfter detailing these facts, I proceeded to show that the nature of 

 the different coats of the seed may be always determined, with certainty, by the relation 

 of one with the other, and from the position they bear in regard to the raphe and the 

 chalaza of the inner integument, and that wherever the raphe is found outside the testa, 

 any tunic exterior to the latter must be of a growth posterior to the development of the 

 orio-inal coats of the ovule. From the position of the raphe in the seeds of Ilagnolia and 

 Talauma, I consequently drew the infaUible deduction, as it appears to me, that the more 

 external fleshy envelope must be arilliform, the thick osseoxis nut must be the testa, and 

 the inner integument with its thickened chalaza must be the true tegmen. 



Since tlie reading of the above memoir, the first volume of that truly excellent work, 

 the ' Flora Indica ' of Dr. Hooker and Dr. Thomson has appeared, in which they detail 

 the nature of the oviter tunics of the seed of Ilagnolia (in p. 73), entirely in accordance 

 with the conclusion of Dr. Asa Gray, but the reasons on which they have adopted this 

 conclusion appear to me to involve some points which materially affect the legitimacy of 

 the inferences there deduced. I cannot agree in their opiuion of the perfect accuracy of 

 the accoimt of the structure of the seed of Magnolia, as given by Gaertner, for though 

 nothing contrary to truth is there stated, yet the most important point which bears on 

 the present discussion, the existence of a raphe, is altogether omitted ; and I feel con- 

 vinced, that if that eminent earpologist had been aware of its existence, he would not 

 have concluded that the outermost eoatiug forms one of the true integuments of the seed, 

 meaning by this term, those which are developments of the primine, secundine, &e. The 

 authors of the ' Flora IncUca ' and the distinguished American professor do not notice the 

 peculiar perforation in the simimit of the crustaceous envelope through which the raphe 

 passes, and they call this extremity the chalaza, a term which, in accordance with Gaert- 

 ner, I think ought always to be restricted to that peculiar thickening of the inner integu- 

 ment around the point where the raphe becomes lost in its substance*. I have minutely 

 described this process of the testa in the seed of Talauma as a distinct perforation which 

 I have called the diapyle ; it is of frequent occurrence in the extremity of the testa of the 

 seeds of different plants, and is destined solely to the purpose just mentioned ; in fact 

 it is the corresponding point in the original base of the primine through which the spiral 

 vessels, represented in the figure of Dr. A. Gray, pass to communicate their nourishing 

 influence to the secimdine, and to the body of the ovule, prior to the commencement of 

 its inversion, and is the only point in the primine in which there exists any passage for 

 these vessels, either before or after the anatropal action, and therefore the only point in 

 the testa (or tunic, resulting purely from the growth of the primine), that could be 

 traversed liy the raphe. The presence of a diapyle in one of the tunics of a seed, is as 

 certain an indication that this is the real testa, as the existence of a chalaza affords the 

 surest proof of the nature of the inner integument. The actuality of the true chalaza, 



* " Chalaza nempe nobis dicitur parva areola saturate colorata, aut tuberculimi parvum spongiosum, aut callosum, 

 quod ex idtimis vasorum umbilicaliura internorum finibus, vel et ex chorii exsuccis reliquiis originem suam traliit, et in 

 siiperficie exteriore membranse seminis intemse conspicitur." — Gcertn. de Fruct., Introd p. 135. 



