278 



Ml', J. Miers on the Nature and 07'i(/in 



sections of an anatropal ovule, b is the placentary sheath, con- 

 taining the nourishing vessels, a, proceeding from the placenta 

 and terminating in the gangylode, f; c is the priraine, d the 

 secundine, e the nucleus. It is here manifest that the nourish- 

 ing vessels enclosed in the placentary sheath never find their 

 way into the tissues of the primine. 



7. We may therefore infer, as an axiom from the three fore- 

 going premises, that the raphe does not primarily, nor does it 

 subsequently exist within the substance of the primine ; and it 

 is equally clear that if any penetration of the vessels of the raphe 

 into its tissues were to exist, the natural course of such entrance 

 would be only through the gangylode or chalazal point of the 

 seed ; but no such extension of the raphe beyond that point has 

 ever been observed. 



8. It is equally clear, in the course of the growth of the tunics 

 of the ovule into the coats of a seed, that if 

 there be no lateral expansion of the placen- 

 tary sheath, then the raphe must be found 

 as a distinct cord or compressed fistular line, 

 remaining adnate to one side of the testa, 

 exhibiting itself in transverse section as in 

 the margin, where a is the bundle of nourish- 

 ing vessels, b the compressed sheath in which it is enclosed, 

 c the testa, d the tegmen. 



9. But if we often find the vessels of the raphe imbedded 

 within the substance of a distinct and entire fleshy coating which 

 completely envelopes the two usual integuments of the seed, 

 then the only conclusion we can draw is, 

 that there has been a growth and exten- 

 sion of the placentary sheath, which has 

 become enlarged into such a thick coat- 

 ing over the entire surface of the testa, 

 as seen in the margin, where a shows 

 the vessels of the raphe, b the extraneous 

 fleshy coating or arilline, c the testa, 

 d the tegmen. The testimony a posteriori 

 presented by the appearances in the seed in this case, combined 

 with the evidence a priori observed in the pre-existing ovule, 

 convey certain proof of the intermediate growth and extension 

 of this extraneous coating, as convincing as that of any demon- 

 stration in Euclid, even if no one had ever witnessed this 

 expansion. 



10. It is manifest that the period of the growth of this extra- 

 neous coating nuist have been subsequent to that of the act of 

 inversion and fertilization of the ovule, and that it is therefore 

 somewhat arilHfonn in its nature. This kind of coating, being 



