256 



ESSENTIAL ORGANS — THE OVULE. 



When, in consequence of the deyelopment on one side, the ovule is 

 so changed that its apex or foramen (fig. 457, 4, n) is brought into 

 close apposition with the hUum (fig. 457, 5, h), and the chalaza is also 



Fig. 458. 



carried round so as to be at the opposite extremity (fig. 457, 5, c), 

 then the ovule becomes inverted, anatropal or anatropous [avar^iiroi, I 

 subvert). In this case (fig. 458) the union of the chalaza, ch, with 

 the nucleus, n, is removed from the hilum, and the connection between 

 the chalaza and placenta is kept up by a vascular 

 cord, r, passing through the funiculus, and called the 

 raphe Qatpfi, a line). The raphe often forms a ridge 

 along one side of the ovule, and it is usually on the 

 side of the ovule next the placenta. Some look upon 

 this kind of ovule as formed by an elongated funiculus 

 (fig. 457, 5, /) folded along the side of the ovule, and 

 becoming adherent to it completely ; and support this 

 view by the case of semi-anatropal ovules, where the 

 funiculus is only, as it were, partially attached along 

 one side, becoming free in the middle ; and also by 

 cases where an anatropal ovule, by the separation of the funiculus from 

 its side, becomes an orthotropal seed. 



The anatropous form of ovule is of very common occurrence, and 

 may probably aid in the process of fertilisation. Ovules which are at 

 first orthotropous, as in Chelidonium majus (fig. 457, 2), sometimes 

 become anatropous in the progress of development (fig. 457, 4). 

 When the ovule is attached to the placenta, so that the hilum is in 

 the middle, and the foramen and chalaza at opposite ends, it becomes 

 transverse, am/phitropal or heterotropal {dfi<pl, around, 'iripog, diverse). 



The position of the ovule relative' to the ovary varies. When 

 there is a single ovule, and with its axis vertical, it may be attached 



Fig. 457. Ovule of Chelidonium majus at different stages of development, h, Hilura or 

 umbilicus, ch, Chalaza. /, Funiculus or umhUical cord, r, Eaphe. n, Nucleus, ti, Se- 

 cundine. te, Primine. ed, Endostome. ex, Exostome. 1, First stage : nucleus still naked. 

 2, Second stage : nucleus covered at its base by the secundine. 3, Thii'd stage : the primine 

 developed and covering the secundine at its base. 4, Fourth stage : the ovule completely 

 reflected, and its point turned downwards. 6, The same cut longitudinally, to show the 

 relation of its different parts. Fig. 458. Anatropous ovule of Dandelion, out vertically. 

 ch, Chalaza. r. Raphe, n. Nucleus. 



