78 



DEVELOPMENT OF PH^ENOGAMOUS PLANTS. 



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

 enwrapped one within 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 downwards 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. Ill"), Oak (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 earlier 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, Iris, Indian Corn, and the like, the embryo 



FIG. 130. Indian Corn 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 emb'-yo 

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



