370 ANOMALOUS PLACENTAE [BOOK i. 



within the margin. In Epiphegus each carpel has two 

 intramarginal placentae, which diverge from the base up- 

 wards, and terminate before reaching the apex. In Lathrsea 

 there is to each valve but one placenta, which may be regarded 

 as two confluent ones occupying the very face of the dorsal 

 suture of the carpel. And finally, in ^Eginetia indica, and I 

 believe in J^ginetia abbreviata also, the placenta is in like 

 manner confined to the axis of the valve, occupying the same 

 position upon the carpels as in Lathrsea, but broken up into 

 a number of parallel plates of unequal depth, over the whole 

 surface of which multitudes of minute seeds are distributed. 

 If we connect these facts, about which there can be no sort 

 of question, with the well-known placentation of Bixads 

 (Flacourtiaceae), Water Lilies (Nymphseacese), and Butomads, 

 we shall find that they invalidate the general carpological 

 rule, that the placentae belong to the ventral suture of a 

 carpel, and consequently alternate with the dorsal; and we 

 shall have to admit that the position of the placentae with 

 regard to the margins of the carpel is reducible to no certain 

 rule, but depends upon specific organisation. Consequently 

 we shall no longer be unable to account for the unusual 

 situation of the placentae opposite the stigma, in Papaver (as 

 M. Kunth. has lately noticed), in Parnassia, or elsewhere.* 



* The position of the placenta in Poppyworts (Papaveracese) has thus been 

 explained by Mr. J. B. Howell : " The simplest state of the capsule in the 

 Papaveracese is exhibited by Bocconia, Linn., in \vhich it consists of two dor- 

 sally-compressed carpels united by their margins, forming a flattened one-celled 

 capsule containing a single seed, which is attached to the inferior part of the 

 replum or annular receptacle formed by the united margins of the carpels, from 

 which the greater portion of the latter separates in the form of valves. This 

 annular receptacle is shown to be identical with true parietal placentas, although, 

 except at a single point at its base, it does not bear ovules, by the latter being 

 developed throughout its entire vertical extent on both sides the capsule in the 

 cognate species, Macleaya cordata, Brown (Bocconia cordata, Linn.) The 

 capsule is crowned by a deeply bifid stigma, whose internally plumose halves 

 being widely reflexed correspond in situation and direction to their subjacent 

 valves, and, therefore, alternate with the intervalvular parietal placentas, 



It is interesting to remark, that in this, the simplest state of the structure of 

 the capsule, the relation of parts exemplifies the law which expresses the neces- 

 sary alternation of stigmas with parietal placentas ; and that it is, therefore, the 

 reverse of that exhibited by the more complex capsules. 



In Macleaya cordatn, the two parietal placentas bear several ovules ; and 

 the lobes of the stigma, though capable of separation, are vertical and in close 



