GROUP IV. — PHANEROGAMIA : ANGIOSPERM^. 



525 



The position of attachment is a point of descriptive importance, 

 more especially where the number of ovules is small, or where there 

 is but one, in the loculus. When the ovule is attached to the top of 

 the carpel, so that it hano-s into the loculus, it is said to he pendulous ; 

 when it is attached high up, but at the side, it is suspended; when 

 it is attached to the side and projects straight, it is horizontal ; 

 when it is attached at the side, but towards the base of the carpel^ 

 and stands up into the loculus, it is ascending. 



FiQ. 338. — Diagrams of the difiFerent modes of Placentation. A Monomerous ovary of 

 Helleborus, opened along the ventral suture; 8 the ovules on (<j) the marginal placenta. 

 B Transverse section of the ovary of Nicotiana : / wall of the ovary ; q placenta, largely 

 developed by the union of the margins of the carpels (axile placentation). C Transverse 

 section of the ovar^' of Butomus. The ovules are scattered over the whole of the inner 

 surface, except the midrib, m (superficial placentation). B Longitudinal section of an 

 ovary of one of the Composite : / the wall ; the erect, anatropous ovule («) grows from Hie 

 base by the side of the apex of the alls, a. E Longitudinal section of the ovary of one of 

 the UmbellifcrBe ; in each chamber an anatropous ovule is suspended. F Longitudinal 

 section of Rheum; a single erect orthotropous ovulo grows at the apex of the floral axis. 

 G Longitudinal section of the ovary of one of the Primulaceae; the ovules grow on a 

 prolongation of the axis (free central placentation). Fig. 336 B represents parietal 

 placentation. 



When the ovules are borne, either actually or apparently, by the 

 axis, the placentation is said to be axial. When many ovules are 

 borne on the axial placenta (as in the Primulaceae, Santalaceae, etc., 

 Fig. 338 G)^ the placentation is termed freecentral. When there 

 is but a single ovule in the loculus, the placentation is basilar or 

 haaalj and the ovule is erect : in this case the ovule is borne either 



