372 Mr. R. Brown on the Plurality and Development 



April 20, 1844. 



Postscript. — It is necessary to notice the recent publication 

 of a very important memoir by MM. de Mirbel and Spach on 

 the development of the embryo in Coniferce'^. 



These excellent observers confirm the principal statements of 

 the preceding essay, with the brief abstract of which only they 

 were acquainted. 



They have also extended the investigation to Thuja and Taxus, 

 two genera which I had not examined, and in which, especially 

 in the latter, the structure appears to be remarkably modified ; 

 and they have ascertained some points in Pinus itself that I had 

 overlooked. 



In this memoir M. de Mirbel refers to his early observations 

 on the structure of the seeds of Cycas which occur in an essay 

 read before the Academy of Sciences in October 1810, and soon 

 after published in the ' Annales du Museum f.' 



These observations and the figures illustrating them clearly 

 prove M. de MirbeFs knowledge of the plurality of embryos in 

 Cycas at that period. And in his recent memoir on Coniferce he 

 regards them as giving the earliest notice of that remarkable 

 structure ; stating also that my first publication on the same sub- 

 ject was in 1835. 



But as the * Prodromus Florae Novse Hollandise* was published 

 before M. de MirbeFs essay in the ' Annales du Museum,' which 

 appears from his references to that work in the essay in question, 

 he must have overlooked the following passages : — 



" In Cycadi angulata puncta arese depressse apicis seminis tot- 

 idem canalibus brevibus respondent gelatina homogenea primum 

 repletis et membrana propria instructis, unico quantum observa- 

 vimus embryonifero, quo augente reliqui mox obliterati sunt." — 

 Prodr. p. 347. 



"Structura huic omnino similis hactenus absque exemplo nee 

 uUa analoga (nempe embryones plures in distinctis cavitatibus 

 ejusdem albuminis) nisi in Cycadi et nonnunquam in Visco cog- 

 nita sit.'' — Prodr. p. 307. 



I may add, that this structure of Cycas was ascertained in 

 living plants on the east and north coasts of New Holland in 1802 

 and 1803. 



The earliest observer of the principal fact, however, was pro- 

 bably the late Aubert du Petit Thouars, who in a dissertation on 

 the structure and affinities of Cycas published in 1804 J, distinctly 

 notices the points on the surface and the corresponding corpus- 

 cula within the apex of the albumen, into which corpuscula he 



* Annales des Sc. Nat. 2 serie, November 1843. 



t Annales du Muoeum d'Hist, Nat. torn. xvi. p. 452. tab. 20. 



I Hiistoive des Vcgctaux des lies d'Atrique, p. 9. tab. 2. n. 



