of Papaveraceae, and on the Stigma of Cruciferae. 249 



be detected, which has never to my knowledge been noticed. 

 This difference will be found of very considerable interest and 

 importance, from its affording an apparent exception to a ge- 

 neral law of great value in systematic botany, and from the 

 assistance which, when rightly understood, it is capable of 

 affording in the elucidation of other obscure and apparently 

 anomalous forms of structure. The peculiarity to which I 

 allude consists in the difference of the relation which the stig- 

 matic rays bear to the dissepiments in the capsules of the 

 Nymphceacece and in the Papaveracece. In the Nymphceacece 

 the stigmatic rays alternate with the ovuliferous dissepiments, 

 in correspondence with the law (hitherto considered intact), 

 that " parietal placentae must alternate with the stigmas ;" 

 whilst in Papaveracece the stigmatic rays are opposite to the 

 dissepiments ! This important differential character, which I 

 detected in 1832, appears not even at this time to be known 

 to those systematists who have written on the natural orders 

 of plants ; at least it is not mentioned by Jussieu, ' Tab. du 

 Regne Veg.,' par Vent. ; Smith, ' Eng. Flora f DeCandolle, 

 'Syst. Nat.' and 'Prodromus;' S. F. Gray, 'Nat. Arrang. 

 Brit. PI. ;' Salisbury, who established the Order Nymphceacece 

 in 'Annals Bot.;' Lindley, ' Int. Nat. Syst.' and 'Synopsis Brit. 

 Fl. ;' Burnett, < Outlines to Bot. ;' Don, < Gen. Syst. Bot. ;' 

 Royle, ' Bot. of Himalayas f Hooker, ' Bot. Mag/ arranged 

 according to natural orders ; nor Drs. Torrey and Asa Gray, 

 ' Flora of North America/ 1 840, which is the latest published 

 systematic work. Indeed, so entirely unaware are even the 

 latest of these writers of the existence of this character, as a 

 differential one, serving to separate by abruptly defined limits 

 those otherwise nearly allied orders, that Lindley, Hooker, and 

 the authors of the * Flora of North America,' in describing the 

 relation of the dissepiments to the stigmas in Papaveracece, in 

 which alone they notice it, describe it wrongly ; the first two 

 writers entirely so, and the latter in part ! Dr. Lindley says, 

 " stigmas alternate with the placentas" (!), which Drs. Torrey 

 and Asa Gray repeat, excepting only Papaver itself, in which 

 they correctly say they are " opposite," and Meconopsis, which 

 they distinguish by a mark of doubt (?). 



There seem to be but two possible modes of accounting for 

 this apparent anomaly in the Papaveracece: — first, that the 

 seminiferous dissepiments are not true placentas formed by 

 the adhesion of the inflected sides of contiguous carpels (which 

 would appear to necessitate their alternation with the stigmas), 

 but are merely projections of cellular tissue forming seminife- 

 rous plates extending into the cavity of the capsule, and pro- 

 ceeding from the centre of the internal face of each of the car- 

 pellary valves. The assumption, however, that ovules may be 



