1224 A TEXTBOOK OF THEORETICAL BOTANY 



been held to show that in such cases the ovarian wall is indeed receptacular 

 up to the level at which these bundles become separated, even if it is appen- 

 dicular above. 



We have no space to follow all the involved arguments which have 

 marked this controversy during at least a hundred years. As it implies the 

 question of the morphological nature of carpels, placentae and ovules, it is 

 obviously a matter of some importance and every kind of evidence has been 

 looked for and usually found. We can only say that weight of evidence, 

 even in the classic case of the Apple, seems to be on the side of the view that 

 the enclosure of the gynoecium in most inferior ovaries is brought about by 

 the concrescence of the lower portions of the outer floral members to a 

 greater or less degree, and their adnation to the ovary wall. There is even 

 the surprising condition in the Dipsacaceae, where in some species the 

 gynoecium is enclosed by a floral tube which is not united to it except at 

 the very top and where the appendicular condition is scarcely open to doubt. 

 The analogous case of Furcraea has been cited on p. 1136. We may also 

 cite Velenovsky's famous Epilobium anomaly, already described on p. 1135. 

 Velenovsky noted that the free surface of the abnormal superior ovary 

 bore hairs exactly like that on the outer surface of the normal inferior ovary 

 from which he inferred that the external tissues in both cases were mor- 

 phologically identical. 



It would be a mistake to assert that circumferential growth of the 

 receptacle never occurs. One can say, however, that in most of the cases 

 where it has been alleged, the alternative explanation of cohesional growth 

 of the floral appendages is possible and in some instances it may be regarded 

 as proved. No case in which this explanation is ruled out has yet been 

 produced. The evidence in favour of receptacular hollowing is weaker 

 than would be supposed from the frequency with which it is invoked. 



To sum up, we may conclude that the receptacle may have played a 

 relatively minor part in the production of inferior ovaries. Although thus 

 leaning towards a not too exclusive acceptance of the appendicular theory, 

 we must recognize that the question remains one for interested considera- 

 tion. 



The mode of attachment of the ovules within the ovary, generally called 

 their placentation, is a matter to which considerable importance is attached 

 in the classification of Angiosperms. The comparative study of the structure 

 of the placentae themselves apart from their vascular supply has, on the 

 other hand, attracted little attention. 



Placentation seems to be a character of some constancy and it is very 

 often uniform throughout whole families, thus being useful in classification. 

 If the carpel is regarded, formally, as a phyllome, then we may say that the 

 ovules are borne either on its margins or on its adaxial side. Only one case 

 of definitely abaxial ovules has been recorded, in Doryanthes (Amarylli- 

 daceae) where they are situated on the abaxial sides of the infolded margins. 

 The exact position in many other cases is obscure. When the carpel or 

 carpels develop singly they usually show the form of an infolded leaf with 



