FORMS AND GROWTH OF SEED 



99 



131. Inverted Seeds. — But sometimes a flower turns 

 over on its stalk, like the snowdrop and harebell, and the 

 same thing often happens to a seed. This gives rise to 

 the inverted, or anatropoits kind (Fig. 223). In this case, 

 which is due to certain peculiarities in the early growth of 

 the seed, the stalk does not remain separate Hke the stem 

 of a pendent flower, but coalesces more 

 or less completely with the coats, and 

 thus forms the rhaphe (Fig. 223), d. The 

 chalaza remains at the base, ch, which is 

 now by inversion at 

 the top ; but as the 

 stalk, or rhaphe, is 

 adherent to the coats, 

 it can not break away 

 at the base, and 

 hence, in anatropous seeds the hilum 

 and micropyle are brought close to- 

 gether, at the real apex of the seed. 

 The adherent stalk, or rhaphe, often 

 becomes reduced to a mere line or 

 groove, as we saw in the cotton and 

 castor bean, or may disappear alto- 

 gether, but the chalaza can generally 

 be distinguished by a tendency of 

 the parts to cohere at that point. 

 Variations in these modes of attachment are shown in 

 Figures 225, 226. In the campylotropous or curved kind, 

 the seed is bent over during early growth into a circular or 

 kidney shape, so that the micropyle is brought into close 



222. — A pendulous 

 flower, showing the 

 inverted position. 



223. — Diagram of an 

 inverted or anatropous 

 seed, showing the parts in 

 section ; a, outer coat ; b, 

 inner coat ; c, nucleus ; 

 d, rhaphe; ch, chalaza; 

 h, hilum ; m, micropyle 

 {after GRAY). 



224 225 22° 227 



224-227. Seeds (GRAY) : 224, orthotropous seed of buckwheat, c, hilum and 



chalaza,/ micropyle; 225, campylotropous seed of a chickweed, c, hilum and 

 chalaza]/' micropyle; 226, amphitropous seed of mallow,/ micropyle, h, hilum, 

 r rhaphe, c, chalaza ; 327, anatropous seed of a violet, the parts lettered as in the last. 



