of Papaveraceae, and on the Stiyma of Cruciferae. 253 



What are the practical bearings of this anatomical pecu- 

 liarity in the stigmas of Papaveraceae ? Observe the assistance 

 it affords in elucidating the hitherto controverted structure of 

 the stigma and capsule of Cruciferae. In this order the variably 

 elongated capsule consists of a single cell with two linear 

 parietal placentas, each of these terminating superiorly in a 

 stigma ! The placentas are occasionally united by an inter- 

 vening membrane, converting the capsule into two cells. 

 When ripe the capsule separates into three parts — two lateral 

 valves and an intervening replum, formed of the persistent 

 parietal placentas, which are crowned by the two permanent 

 stigmas ! 



Dr. Brown appears to have been the first to establish a 

 general principle for explaining the structure of complex cap- 

 sules ; his words are, " Capsulas omnes pluriloculares e 

 totidem thecis conferruminatas esse, diversas solum modis 

 gradibusque variis cohaesionis et solubilitatis partium judico," 

 c Prod. Fl. Nov. Roll./ p. 558, ] 810. In 1818, < Linn. Trans./ 

 he applied this principle to the explanation of the seed-vessel 

 of the Composite, and showed its one-seeded achenium to be 

 an extreme state of simplification of an organ arising from 

 deprivation of parts^ and to be in reality a bi-carpellary cap- 

 sule, in which only a single seed is developed on one parietal 

 placenta and none on the other — the parietal placentas being 

 represented by two delicate cords ; and referred also to Boc- 

 conia, as an analogous instance in Papaveraceae ; and likewise 

 to Proteaceae, for other instances illustrative of the successively 

 increasing imperfection which leads from the normal type to 

 the most anomalous conditions. In 1821, DeCandolle, in a 

 memoir on the Cruciferae, ( Annales du Museum/ and in the 

 article on the same family in f Systema Naturale/ described 

 the capsule in strict conformity with the principles of Brown 

 (without acknowledging himself indebted to the latter), as 

 being composed of two carpels whose corresponding inflected 

 margins formed the parietal placentas ; the bi-carpellary ori- 

 gin of each placenta being indicated by its bearing a double 

 row of ovules. [See diagram of structure of the silique in 

 DeCandolle's Memoir.] In 1826, Brown, in c Appendix to 

 Denham's Voyage/ p. 217, having substantiated his claim to 

 priority of discovery of the bi-carpellary nature of the capsule 

 of Cruciferae, by referring to his observations of 1810 and 

 1818, as quoted above, and having absolved DeCandolle from 

 any charge of plagiarism, further proved the double nature of 

 the placentas and dissepiment, by showing that the two la- 

 mellae of which the latter is composed are frequently separa- 

 ble, and that when this is not the case, the constituent lamellae 

 are rendered evident by the want of correspondence of their 



