21S COMPOUND ORGANS OF PLANTS. 



the embryo of the bean, the pea, or the oak, we shall see a coty- 

 ledonary body formed of two cotyledons. The embryo which 

 presents such a conformation is a Dicotyledonous embryo. If, 

 on the contrary, we examine the embryo of the wheat or the 

 maize, of the iris or the palm, we shall find a simple coty- 

 ledonary body, formed by a single cotyledon. The embryo 

 in this instance is termed a monocotyledonous embryo. 

 The character drawn from the number of cotyledons is of the 

 highest importance, because it divides all phenogamous plants, 

 or those which are provided with flowers properly speaking, 

 into two grand branches, the Monocotyledons and the Dicoty 

 ledons, which differ not only in the structure of their embryo, 

 but in the special organization of all their other parts. 



A certain number of Phanerogamous plants are, however, 

 apparently exceptions in the structure of their embryo to these 

 two grand divisions. The cone-bearing plants, for example, 

 such as the spruce, fir, and larch, have not one or two, but 

 sometimes six, nine, twelve and even fifteen verticillate cotyle- 

 dons, which resemble in their linear form and verticillate 

 arrangement, the clustered and fascicled leaves of the larch. 

 To such embryos the term polycotyledonous has been applied, 

 but M. Duchatre has proved that these polycotyledonous 

 embryos are only Dicotyledonous embryos, whose two cotyle- 

 dons are deeply divided into a number of segments. Therefore, 

 it is proper to retain them among the Dicotyledonous embryos 

 of which they are only a variety. 



In exalbuminous embryos, that is to say, those which are 

 immediately covered by the episperm or seed coat, the cotyle- 

 dons are excessively thick and fleshy, and their albuminous 

 contents furnish to the young and germinating embryo the 

 first materials of its nutrition. In such seeds as are albumi- 



