62 



STRUCTURAL BOTANY. 



been known to perfoim long voyages without injury to their vitality. Squirrels laying 

 up their winter stores in the earth ; birds migrating from clime to clime and from island 

 to island, in like manner conspire to effect the same important end. 



Review. 172. What is the seed? Its two coverings. 173. The texture of the testa. 

 Its appendages. What is cotton ? 174. Distinguish coma from pappus. 175. What is 

 the aril? 17(5. Positions of the seed in the cell. When is a seed anatropons? Orth6tro- 

 pous? etc. 177. Define hilum. When does a raphe exist ? What is the micropyle? 178. 

 Constituents of an albuminous seed Exalbuminous. 179. Varying proportions of albu- 

 men. Various texture. 180. Distinguish the three parts of the embryo. Where is the 

 food for the embryo ? 181. Distinguish the Monocotyledouous Plants. 182. The Dicoty- 

 ledonous. 183. Position of the embryo in the seed of Violet? Of Pink? Hop? Shep- 

 herd's Purse ? Arabis ? 185. Vitality of the seed. 186. Special arrangements for their 

 dispersion. 



CHAPTER XIII. 



GERMINATION. 



188. The recommencement of growth in the seed is called 

 germination. It is the awakening of the embryo from its tor- 

 por, and the beginning of development in its parts already 

 formed, so as to become a plant like its parent. 



218 



222 



1 



221 I 



Germination of the Beechnut. 21&, Cross-section, showing the folded cotyledons. 219, The radicle 

 only. 220. The ascending axis, above c, appears. 221, The cotyledons expand into the primordial 

 leaves. 222, The first true leaves. 



XS9. All the stages of this interesting process may be conveniently observed, at any 

 season, by an experiment. Let a few seeds, as of flax, cotton, wheat, pea, b3 enveloped 

 in a lock of cotton resting upon water in a bulb-glass, and kept constantly at a proper tern 

 pcratnro. Or. in Spring, the garden-soil will give us examples of all kinds everywhere. 



