Germination 



27 



fleshy, as in the Bean (fig. i) and Acorn, they remain within 

 the seed during germination, finally perishing afi;er the food- 

 material contained in them has been used up for the growth of 

 the embryo. In the case of the Cress, Cabbage, and Beech 

 we have an exalbuminous seed where the cotyledons are thin, 

 and here they rise out of the soil to form the first leaves, carry- 

 ing the testa with them {^g. 43). The Castor-oil plant has an 

 albuminous seed ; in this case the cotyledons are not liberated 

 until after the endosperm has been all absorbed (fig. 42). In 

 the case of the Pine we have an analogous growth (fig. 44), 



Fig. 46. — Lon^tudinal section of fruit of Zea 

 Mais, c, rericarp_ ; n, remains of the stigma ; 

 Js, base of the fruit ; eg^, hard yellowish part 

 of endosperm ; ew, white softer portion of 

 endosperm ; sc, seutellum (cotyledon) of 

 embryo ; ss, its apex ; e, its epidermis ; k, 

 plumule ; u/ (below), the main root ; lus, 

 sheath covering main root ; w (above), 

 lateral rootlets springing from the first inter- 

 node of the stem, st. (After Sachs.) 



Fig. 47. — Germinating 

 embryo of Oat (the 

 endosperm removed). 

 /, the plumule ; s, the 

 seutellum ; r, r, the 

 rootlets ; co, the coleo- 

 rhiza. 



the cotyledons (which are numerous) appearing above ground 

 after the absorption of the albumen, the peculiarity here being 

 the development of chlorophyll in the cotyledons before they 

 rise above the surface. All these are dicotyledonous seeds. 

 The remaining two illustrate the germination of monocotyledons. 



