JF THE EMBRYO AND SEEDLING. 



CHAPTER II. 



MORPHOLOGY AND DEVELOPMENT OF THE EMBRYO AND 



SEEDLING. 



19. The Embryo is the initial plant, originated in the seed. 1 

 In some seeds it is so simple and rudimentary as to have no 

 visible distinction of parts : in others, these parts may have 

 assumed forms which disguise their proper character. But every 

 well-developed embryo essentially consists of a nascent axis, or 

 stem, bearing at one end a nascent leaf or leaves, or what an- 

 swers to these, while from the other and naked end a root is 

 normally to be produced. This stem is the primitive internode 

 of the plant : its leaf or pair of leaves is that of the first node. 

 The plant therefore begins as a single phytomer. Some embrj'os 

 are no more than this, even when they have completed their 

 proper germination : others have taken a further development 

 in the seed itself, and exhibit the rudiments of one or more fol- 

 lowing phytomera. The embryo of the Maple is an example of 

 the first kind ; and, being large enough for handling and for the 

 display of all its parts to the naked eye, and the character of 

 these parts being manifest even in the seed, it is a good subject 

 with which to commence this study. And for this the Sugar- 

 Maple is one of the best of 

 the Maples. Its embryo 

 (seen in Fig. 2 in the coiled 

 condition which it occupies 

 in the seed, and in Fig. 3 

 and Fig. 4 uncoiling and be- 

 ginning to grow) is an initial stem, bearing a pair of leaves, and 

 nothing more. These parts take the technical names of 



1 Normally a seed contains a single embryo. Polyembry, the formation of 

 two or more embryos, occurs occasionally as a kind of superfoetation in 

 some seeds. In those of the cultivated Orange it is most common, and an 

 evident monstrosity. In Coniferae and Loranthaceae, two or three embryos, 

 of equal size and perfection, are not rarely produced. 



FIG. 2. Embryo of Sugar Maple, in vertical section, as coiled in the seed, merely 

 somewhat loosened. 3. Embryo of same, just beginning to unfold in germination. 

 4. Same more advanced : a. its stem or caulicle ; bb. its two leaves or cotyledons. 



