78 



DEVELOPMENT OF PHiENOGAMOUS PLANTS. 



embryo, with a strong and well-developed plumule, of several leaves 

 enwrapped one witliin another ; and, being amply nourished by the 



copious mealy albumen, it sprouts with re- 

 markable vigor, sending up three or four 

 leaves in rapid succession before the earliest 

 has completed its growth, at the same time 

 sending forth additional roots downwai-ds into 

 the soil. Here also, as in the Pea and the 

 Oak, &c. (124) the germination is hypogcEous, 

 the cotyledons remaining in the seed under 

 ground, and the leaves which 

 appear above ground belonging 

 to the plumule. This is also the/ 

 case in the Iris (Fig. 132) and 

 most plants of the same class. 

 But in the Onion the co- 

 tyledon (which is single) 

 lengthens, raises the seed 

 out of the ground, and be- 

 comes the first leaf. 



127. In Indian Corn (Fig. 

 130), in Iris (Fig. 132), and 

 also in the germinating Cher- 

 ry (Fig. IIP), Oak (Fig. 

 121), and Pea (Fig. 119), the leaves of the plumule 

 succeed one another singly, that is, there is only one 

 upon each joint of stem : in other words, the leaves are 

 alternate. Whereas in the seedling Beech and the Bean 

 (Fig. 114, 117) these early leaves are in pairs, that is, 

 are opposite. A similar difference is to be noticed in the 

 embryo as to the 



128. Number of Cotyledons. All the earher illustra- 

 tions are taken from plants which have a pair of cotyle- 

 dons, or seed-leaves, belonging to the first joint of stem, 

 that is, to the radicle. Such embryos are accordingly 

 said to be Dicotyledonous, — a name expressive of this fact. 

 But in the Lily, Onion, L'is, Indian Corn, and the hke, the embryo 



FIG. 130. Indian Com more advanced in germination, and with a cluster of roots. 

 FIG. 131. Section of a seed of Iris or Flower-de-Luce, magnified, showing the small ejnbrj'O 

 enclosed in the albumen, near its base. 132. Germinating plantlet of Iris. 



