193 Mr. B. Clarke on Relative Position ; 



of that number, the additional series being frequently reduced 

 by abortion or non-development in the same manner as the first, 

 thus giving rise to the formation of ovaries with five or four 

 carpels. And as tricarpous ovaries in Exogens have generally 

 two carpels lateral and one posterior, it might be supposed that 

 ovaries having a greater or a less number of carpels would, if 

 they became tricarpous, have the three carpels so placed. There 

 are, however, exceptions to this rule, of which Viola, Fagus and 

 Menispermum are instances, where the carpels are two of them 

 lateral and one anterior ; and in other instances the three carpels 

 vary in their position in the same plant, as in Clethra, Pitto- 

 sporum and Delphinium. In Endogens the position of the three 

 carpels is perhaps less regular, as Dioscoi'ea, Maranta, Phoenix, 

 and others have them placed as in Viola or irregularly, the irre- 

 gularity being apparently the consequence of the ovary being 

 turned on its axis so that a lateral carpel becomes anterior. 



Value of the Characters. 



From the Tables as they now stand, the following inferences 

 are deducible* : — 



1. That the position of cai-pels when two, right and left of the 

 axis, is common to all subdivisions, but predominates in the 

 Heterocarpous Division, where the position of the single carpel 

 is for the most part different from flower to flower, and generally 

 variable to the greatest degree. 



3. That species with carpels anterior and posterior also occur 

 in all subdivisions, but that this arrangement obtains more ge- 

 nerally in the division designated as Proterocarpous, from the 

 single carpel being usually anterior, and from the ovaries when 

 dicarpous not unfrequently exhibiting a tendency to suppression 

 of the posterior cell. 



3. But that in plants with irregular flowers or didynamous 

 stamens, the position of the cai-pels when two is constant, and 

 with very few exceptions anterior and posterior. 



4. That a certain portion of the class Exogens never has the 

 single carpel posterior. 



5. That a single carpel lateral may possibly occur in all sub- 

 divisions, but that this character does not, among Heterocarpous 

 plants, extend through an entire family, unless Nyctagineae should 

 prove to be an exception. 



As however the position of the single carpel in many families 

 remains to be ascertained, some changes will doubtless have to 



* Since the formation of the Tables, it has been found that part of the 

 details are obUged to be omitted in the printing, but those most deserving 

 notice are contained in Part III. 



