326 



ORGANOGRAPHY. 



which are commonly distinguished by special names ; but there 

 are two others, which appear to be but slight modifications of 

 the anatropous ovule, to which the names of amphitropous and 

 semi-anatropot(,s have been respectively given. The amphitro- 

 pous, or, as it is also called, heterotropous or transverse ovule, is 

 produced when the hilum, /, is one side of the ovule, and the 

 micropyle, m, and chalaza, ch, placed transversely to it {fig. 

 727). In this case the hilum is connected to the chalaza by 

 a short raphe, r. In the senii-anatropoiis ovule the relative 

 position of the parts is the same {fig. 726), but the funiculus, 

 /, is here parallel to the ovule, instead of being at right angles 

 "to it. 



The further development of the ovule will be described here- 

 after under the head of Eeproduction of Phanerogamous Plants. 



2. THE SEED. 



The seed is the impregnated ovule. Like the ovule, it is 

 either attached directly to the placenta, in which case it is sessile, 

 or by means of a stalk, called i\iQ funiculus {fig. 728,/); its 

 point of attachment is also termed the 

 hilum or timbiliciis. The position of 

 this hilum may be commonly seen on 

 seeds which have separated from the 

 funiculus or placenta, by the presence 

 of a scar, or in a difference of colour to 

 the surrounding integuments. The hi- 

 lum varies much in size, being some- 

 times very minute, while in other cases 

 it extends for some distance over the 

 surface of the integuments, as in the 

 Horse-Chestnut and Mticuna. The 

 centre of the hilum, through which the 

 nourishing vessels pass, has been called 

 the omphalodium. The hilum, as in 

 the ovule, indicates the base of the 

 seed, while the apex is represented by 

 the chalaza. This chalaza {fig. 728, ch) 

 is generally more evident in the seed 

 than in the ovule, and is frequently of 

 a dififerent colour. It is well seen in 

 the Orange, and commonly in anatro- 

 pous seeas, in which case also the raphe may be generally 

 noticed forming a projection on the face of the seed. 



The micropyle also, although smaller and less distinct than 

 in the ovule, owing to a contraction of the surrounding parts, 

 may be observed on the seed {fig. 728, m). The detection of 



rap 



Fig. 728. The seed of a 

 Pea, with its integuments 

 removed on one side. pi. 

 Placenta. /. Funiculus. 

 rap. Raphe, ch. Chalaza. 

 m. Micropyle. te. Testa 

 or episperni. e. Endo- 

 pleura. The part within 

 the endopleura is the 

 nucleus of the seed, and 

 Is formed of cotyledons, c, 

 gemmule or plumule, g, 

 radicle, r, and t stalk or 

 tigelle between the plu- 

 mule and radicle. 



