ESSENTIAL ORGANS — THE OVULE. 



257 



to the placenta at the base of the ovary (basal placenta), and it is then 

 erect, as in Polygonaoeae and CompositaB (fig. 459) ; or it may be 

 inserted a little above the base, on a parietal placenta, with its apex 

 upwards (fig. 460), and then is ascending, as in Parietaria. It may 

 hang from an apicilar placenta at the summit of the ovary, its apex 

 being directed downwards, and is inverted or pendulous, as in Hippuris 

 vulgaris (461), or from a parietal placenta near the summit, and then 

 is suspended, as in Daphne Mezereum (fig. 462), Polygalacese, and 



Fig. 459. 



Fig. 460. 



Fig. 162. 



Euphorbiaceae. Sometimes a long funiculus arises from a basal pla- 

 centa, reaches the summit of the ovary, and there bending over 

 suspends the ovule, as in Armeria ; at other times the hilum or 

 organic base appears to be in the middle, and the ovule becomes 

 horizontal, peltate (pelia, a shield), or peritropous ('rtigl, around, and 

 r^intdi, I turn). AH these modifications are determined by the rela- 

 tive position of the hilum and foramen, the length of the funiculus, 

 and its adhesion, as well as the position of the placenta. 



When there are two ovules in the same cell, they may be either 

 collateral, that is, placed side by side (fig. 463), or the one may be erect 

 and the other inverted, as in some species of Spiraea and jEscuIus 

 (fig. 464), or they may be placed one above another, each directed 

 similarly. Such is also the case with ovaries containing a moderate 

 or definite number of ovules. Thus, in the ovary of Leguminous 

 plants (fig. 465), the ovules, o, are attached to the extended marginal 

 placenta, one above the other, forming usually two parallel rows 

 corresponding to each margin of the carpel. When the. ovules are 

 definite (uniform, and can be counted), it is usual to find their attach- 



Figs. 459-462. Carpels belonging to different flowers, cut vertically to show the various 

 directions of the solitary ovule, o, contained in them. /, Funiculus, r. Raphe, c, Chalaza. 

 s. Base of the style. Fig. 459. Carpel of Senecio vulgaris, with a straight or erect ana- 

 tropous ovule. Fig. 460. Carpel of Parietaria oticinalis (pellltory), vrith an ascending 

 orthotropous ovule. Fig. 461. Carpel of Hippuris vulgaris (mare's-tail), with a reversed 

 or pendulous anatropous ovule. Fig. 462. Carpel of Daphne Mezerexun, with a suspended 

 anatropous ovule. 



S 



