uf the External Coatings of Seeds. 281 



it woiiKl bi- impossible to assign any reasonable cause why the 

 inner moiety of that tissue became solidified, while its exterior 

 half escaped tlie same operation. 



Dr. A. Gray suspects that 1 have " formed a wrong idea of the 

 raphe*," and that I have "mistaken for the raphe in Magnolia 

 the cord of vessels it contains ;" and yet in a preceding pagef 

 he designates that cord (the only one existing in that seed) as 

 the " conspicuous cord of the vessels of the raphe," and so figures 

 it as I have done : this is an incongruity only attributable to a 

 lapsus calami. The structure of the seed of Pceonia (as demon- 

 strated in my paper) quite conforms with the views I have here 

 entertained. 



Dr. A. Gray, having watched the increment of the ovule, with- 

 out being able to detect the growth of any extraneous coating 

 over it, complains that this circumstance has not received its due 

 weight J ; but I suggest, in fairness, how far a negative observa- 

 tion can be expected to preponderate against the positive testi- 

 mony of the several high authorities who have witnessed and 

 recorded similar developments. Having quoted some of these 

 on a former occasion §, I need not here allude to the facts ob- 

 served by Dr. Planchon, showing the successive growth of an 

 analogous coating over the seed of Euonymus ; also the gradual 

 production of a similar tunic in the seeds of Opuntia ; and, again, 

 the progressive appearance of the same kind of fleshy envelope 

 in Clusia. I also cited the minute details of Gaspavini, who 

 witnessed the same fact in Opuntia in the several stages of its 

 growth. No one will feel disposed to question the still higher 

 authority of the celebrated ^lirbel, who minutely describes and 

 figures this "production nouvelle," consisting of " deux couches 

 de tissu cellulaire, qui n^aj)partient pas primitivemeut a I'ovule, 

 mais qui s'applique a sa surface et finit par lui servir d'enveloppe 

 comme ses tegumens propres." In this discussion we should 

 not confine ourselves to the single case of Magnolia, but ought 

 to be guided by analogy in other instances. 

 With this view, I pointed to examples, such as 

 Zanonia and Feuillaa, as types of numerous 

 cases where the extraneous coating over the 

 testa is membranaceous and expanded, and 

 which cannot come under the category of a 

 " baccate testa." I also alluded to the tunic 

 in Tacsonia\\, where the osseous testa of the 

 seed is enclosed within a free, reticulated, 

 membranous sac, upon which the cord of the 



* Jouin. Linn. Proc. ii. 110. f Jhid. p. 108. 



+ Ibid. ii. 107. § Linn. Trans, xxii f'7- 



II Linn. Trans, xxii. JW. 



