SEED. 



107 



ascending seeds. . Thus, the Nettle (fig. 578) has an erect seed and a superior radicle; the 

 axis of the seed is straight, the radicular end being furthest from the cotyledonary, 

 which answers to the hilum. In the Sage (fig. 579) and Chicory (fig. 580), the 

 seed is erect, with an inferior radicle; here the embryo seems to have twisted half 

 round upon itself; the cotyledonaiy end, which ought to answer to the hilum, being 

 at the opposite extremity, and the radicle nearly occupying its place ; this movement 

 has taken place in the cavity of the ovule before fertilization, as we shall presently 

 explain ; the result is a long raphe, which runs along one side of the seed, and the 

 chalaza is consequently diametrically opposite to the hilum. The radicle is centri- 

 petal (r. centripeta) when it faces the central axis of the fruit (Lily, fig. 584) ; centri- 

 fugal (r. centrifuga), when it faces the circumference (Mignonette, fig. 384). The 



686. Wallflower. 



Seed cut 

 vertically (mag.). 



587. Lychnis. 



Seed cut 

 vertically (mag.). 



588. Datura. 



Seed cut 

 vertically (mag.). 



589. Marvel of Peru. 



Fruit 

 cut vertically. 



591. Plantain. 

 Ventral surface 

 of seed (mag.). 



592. Plantain. 



Seed cut 

 vertically (mag.). 



embryo is antitropal (e. antitropus), when, its axis being straight, the micropyle (and 

 radicle) is furthest from the hilum (Nettle, fig. 578 ; Rumex, fig. 644) ; it is homo- 

 tropal (e. homotropus) when, its axis being straight, the micropyle (and radicle) is next 

 the hilum, while the chalaza (and cotyledonary end) is distant from the hilum, and 

 only connected with it by a raphe ; then the base of the seed (hilum) and of the 

 embryo (radicle) correspond (whence the term homotropal, Sage, fig. 579; Chicory, 

 fig. 580 ; Pear, Apricot, Rose, Strawberry, Scabious, Centranthus, Campanula, Hearts- 

 ease, Iris, &c.). The embryo is amphitropal (e. amphitropus) when, its axis being bent, 

 the micropyle and chalaza are both close to the hilum (Wallflower, fig. 586 ; Lychnis, 



fig. 587 ; Datura, fig. 588 ; Marvel of Peru, fig. 589 ; 

 Mulberry, fig. 590). The embryo is heterotropal 

 (e. heterotropus) when, from the unequal growth of the 

 coats, neither extremity of the embryo corresponds 

 to the hilum, and the radicle does not correspond 



59C. Pine. 

 Seed. 



590. Mulberry. 



Ovary cut 

 vertically (mag.). 



594. Asparagus. 



Seed cut 

 vertically (mag.). 



595. Spergularia 

 Seed (mag.). 



to the micropyle ; in this case, the axis of the embryo is sometimes parallel to 

 the plane of the hilum (Pimpernel, Plantain, figs. 591, 592), sometimes oblique to it 

 (Wheat, Chamcerops, fig. 593 ; Asparagus, fig. 594) ; the radicle is then said to be 

 eccentric (r. vaga, excentrica). 



