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. After 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 
original coats of the ovule. From the position of the raphe in the seeds of Magnolia and 
Talawma, I consequently drew the infallible deduction, as it appears to me, that the more 
external fleshy envelope must be arilliform, the thick osseous nut must be the testa, and 
the inner integument with its thickened chalazå must be the true tegmen. 
Since the 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 outer tunics of the seed of Magnolia (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 legitimaey of 
the inferences there deduced. I cannot agree in their opinion of the perfect accuracy of 
the account of the structure of the seed of Magnolia, as given by Gærtner, 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 carpologist had been aware of its existence, he would not 
have concluded that the outermost coating 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 Indica’ and the distinguished American professor do not notice the 
peculiar perforation in the summit of the crustaceous envelope through which the raphe 
passes, and they call this extremity the chalaza, a term which, in accordance with Gært- 
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 Talawma 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 secundine, 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 by 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 saturatè colorata, aut tuberculum parvum spongiosum, aut callosum, 
quod | din vasorum umbilicalium internorum finibus, vel et ex chorii exsuccis reliquiis originem hit, et in 
'Perheie exteriore membranæ seminis interna conspicitur.”—Gærtn. de Fruct., Introd. p. 135. 
