150 Linnaan Society. 



in l-carpellary ovaries of Myrtacea, Onagraria, Poly galea, Legumi- 

 noscE and Acanthacece, to which may probably be added Hippurideee, 

 Bruniacete, &c. ; 2ndly, posterior, as in the l-carpellary ovaries of 

 Houttuynia cordata and Piperacea; ; 3rdly, lateral or oblique, instances 

 of which occur in Morece, in Elatostemma, and in Celtidea. The 

 normal number of carpella in all ovaries he regards as three or a 

 multiple of three ; the additional series being frequently reduced 

 by abortion in the same manner as the first, and thus giving rise to 

 the formation of ovaries with four and five carpella. Tricarpous 

 ovaries generally have their component parts placed two laterally 

 and one posteriorly ; but exceptions to this rule occur, as for exam- 

 ple in Viola, where the third carpellum is anterior, and in Clethra, 

 Pittosporum and Delphinium, in which the position of the carpella 

 varies in the same plant. 



Mr. Clarke next proceeds to consider the value of the characters 

 derived from the position of the carpella, for which purpose he has 

 framed a large table containing the results of long- continued ob- 

 servations on a multitude of exogenous plants with monocarpous or 

 dicarpous ovaries. In this table he constitutes two primary divisions, 

 viz. Prot er acarpous , in which the carpella when single are anterior 

 or lateral, never posterior ; and Heterocarpous, in which the single 

 carpellum is for the most part a mixture of lateral, anterior and 

 posterior, and is rarely wholly posterior. The position of the com- 

 ponent parts of the dicarpous ovarium also appears to be more per- 

 manent in the first than in the second division. From this table 

 Mr. Clarke deduces various inferences in relation to the systematic 

 arrangement of plants, and the importance of the characters derived 

 from the position of the carpella, and more especially from that of 

 the single carpellum, which is liable to fewer and less important 

 exceptions. Thus for instance he considers the posterior position of 

 the single carpellum of Ceratophylleee, corresponding as it does with 

 that of PiperacecE and their allies, and differing as far as known from 

 that of any other order with which it could be associated, as a strong 

 argument of affinity. He refers to the case of two-ceUed ovaries 

 with unequal cells, and regards the superior development of the 

 larger cell or of the corresponding stigma as indicative of what would 

 be the position of the single carpellum, were the ovary to be so 

 reduced. These remarks are followed by observations on the 

 general character of his divisions and subdivisions, and by some 

 notes on the position of carpella as regards endogenous plants and 

 Rhizanthece, and on the relation of didynamous stamens and carpella 

 as regards their order of suppression ; and the first part of the 

 memoir concludes with some remarks on the difficulty of determining 

 with precision the true axis of the inflorescence, and the means of 

 obviating this difficulty in certain cases. 



The second part of the memoir is more especially devoted to the 

 consideration of ovaries consisting of a single carpellum, to the rela- 

 tions borne by this carpellum to the axis in various families referred 

 by the author to each of his two principal divisions, and to the 

 grounds from which this relation is deduced. This being entirely 



