of the I 'egeiable Ovule. 25 



cular support is close to the summit of the cell, then the pres- 

 sure of growth causes the ovule to be forced round gradually 

 upon its funicle till it becomes pendent, with its raphe in a 

 dorsal position. In both these instances of resupination of the 

 ovule, there is no removal of the mouths of the tunics from 

 their close contiguity to thetelae conductrices, — a very import- 

 ant feature in the history of its development. These two con- 

 ditions of growth of the placentary sheath may be expressed by 

 the terms epipyla and liypopyla, — the former from iirl super, 

 ttuXt] porta, where the first development is upwards ; and the 

 latter from vtto et ttvXtj, where it shows itself on the lower side 

 of the sheath. In the first condition (where the micropyle 

 points upwards), we have an ovulum anatropum epipylum, or a 

 pendent ovule with a ventral raphe; but where the same ovule 

 becomes inverted by pressure, we have an ovulum epipylum 

 resupinatum, or an ascending ovule with a dorsal raphe. Under 

 the second condition (where the micropyle points downwards), 

 we have an ovulum anatropum hypopylum, or an ascending- 

 ovule with a ventral raphe ; but when this becomes inverted 

 by pressure, it is an ovulum hypopylum resupinatum, or a pendent 

 ovule with a dorsal raphe. It often happens, where numerous 

 ovules issue from a placenta of limited extent, that we have erect, 

 horizontal, and pendent ovules all crowded together, some with 

 a ventral, others with a dorsal raphe ; but it will be found that 

 all are equally epipylous or equally hypopylous, the one series 

 showing their raphes in their normal position, the second inter- 

 mediately placed, while the third, by their resupination, have a 

 dorsal raphe. Under the third condition, where the ovules are 

 in collateral pairs, and where the earliest appearance of the 

 nucleus is upon the lateral face of the placentary sheath, the 

 raphes face one another, whether the subsequent direction of the 

 ovule, by the pressure of growth, be pendent, horizontal, or 

 ascending : this kind of development may be called allopylar if 

 in a single ovule, and heteropylar when in collateral pairs. 



Another consideration worthy of attention in the development 

 of the ovule, is the position of the embryo in regard to the seminal 

 tunics, — that is to say, whether one of the faces of the cotyledons, 

 or whether its margins be placed opposite the raphe : this point 

 has seldom been regarded, except where the embryo is amphi- 

 tropal or campylotropal, in which cases this position is known, 

 from the radicle being said to be incumbent or accumbent in 

 regard to the cotyledons. This relative position is often a con- 

 stant feature in certain families, while in others it is subject to 

 much variation, as in Rhamnacece ; and the character is even 

 sometimes variable in the same genus, as in Rhamnus. The 

 position of the face of the cotyledon in regard to the axis of the 



