Mr. J. Miers on the Affinities of the Olacaceae. 181 



know it to be in other cases, is probably due to adventitious 

 causes. We have every reason to believe, that the development of 

 the ovule and its embryo in the Olacacea is analogous to what 

 has been observed in Santalacece : assuredly the early growth 

 of the ovules is effected under the same peculiar circumstances, 

 and in the seeds of Liriosma, Ximenia, &c., the albumen appeal's 

 naked, or at least, their only covering is reduced to a thin mem- 

 brane, which in the dried state remains more or less attached to 

 the inner surface of the putamen. The phsenomenon of the deve- 

 lopment of these, which I have proposed to call exutive seeds (see 

 last note), has been frequently observed by many eminent physio- 

 logical botanists, moi-e particularly by Mirbel, Schleiden, Meyen, 

 Decaisne, and Griffith. The latter has shown, that among the 

 changes that take place in these cases, is the constant prolonga- 

 tion of the embryonary sac, outside of the "nucleus*," or body 

 of the ovule, and that it is cuiious to witness the rapidity ^vith 

 which this exserted portion grows, and here becomes filled with 

 albuminous tissue : another result being the incorporation of the 

 remaining portion of the sac with that tissue. A similar pro- 

 longation of the embryo-sac was also noticed by the same accu- 

 rate observer in Aviceimiaf, and he infers that this phsenomenon 

 has only been remarked in cases associated with a particular form 

 of free central placenta J ; but this is not correct, for we have 

 evidence, that its occurrence is not constant among the Ciono- 

 sperma. We know Hkewise, from the observations of Mr. Griffith 

 himself, that the same occurs in Congea, Loranthus, &c. Dr. Plan- 

 chon also has minutely described a similar phsenomenon in the 

 seeds of Veronica^, where the embiyo is formed without the 

 usual integuments, and remains covered merely by its embryo- 

 sac, that protrudes outside the main body of the ovule, improperly 

 called the " nucleus," and which afterwards shrivels into the form 

 of a secondaiy funicular cord : in these instances the embryonary 

 sac becomes thickened, and assumes the appearance of a peri- 

 spermal covering around the albumen of the seed, very different 

 in its origin from the true testa of indutive seeds. 



* This terra, though generally used in this case by botanists, is manifestly 

 incoiTect, and has been employed only because it is applied to the identical 

 body which is enclosed within its several tunics in orcUnar}- seeds ; it leads 

 to misconception, because it is difficult to imagine the " nucleus " can mean 

 the external covering of the ovule, while the protruding real nucleary body 

 becomes the entire seed. It would be more conformable to fact, and render 

 the details of the phsenomena more intelligible, to denominate the former, 

 what it really is, the external body of the ovule, and not a '' nucleus." 



t Linn. Trans, vol. xx. p. 2. 



X Ibid. p. 3. 



§ Memoire sur les de'veloppemeus et les caracteres des vrais et faux arilles. 

 Montpelier, 1844. 



