Classification of Plants 1 97 



1. The embryo of a Monocotyledon has one terminal 

 cotyledon with the plumule at one side, while that of a Di- 

 cotyledon has usually two cotyledons on opposite sides of a 

 terminal plumule. Endosperm is usually present in Mono- 

 cotyledons while it is usually absent in Dicotyledons. 



2. In a Monocotyledon, the prophyll or first leaf on a 

 branch is placed on the side toward the main axis. In Di- 

 cotyledons there are two prophylls placed opposite to one 

 another on the sides of the branch. 



3. The stem of a Monocotyledon has numerous bundles 

 which though arranged more or less in concentric circles ap- 

 pear to be scattered, while the primary bundles or leaf traces 

 in a Dicotyledon are few and lie in a ring. In the former the 

 bundles are closed, i.e. the cambium all passes over into per- 

 manent tissue while in Dicotyledons cambium between the 

 wood and bast remains active and the bundles are open. 



4. Leaves of a Monocotyledon are as a rule simple and ex- 

 stipulate with large sheathing bases. The main veins which 

 are usually parallel are united by small cross veins and the 

 margins are entire. In Dicotyledons the leaves which are often 

 compound, generally have a petiole ; they may also have 

 stipules ; the veinlets end freely and the margins are often 

 notched. 



5. The floral structure of a Monocotyledon usually con- 

 sists of five whorls of three parts each and the floral diagram 

 may be represented thus : K?z, C/z, Kn + /?, Qin where ti equals 

 three.^ 



That of Dicotyledons may have five or four (or fewer) 

 members in a whorl and the floral formula may be represented 

 thus : K;?, Qn^ Kti + ?i (or fi) Gn (or fewer) where n equals five, 

 four, or fewer. 



In learning to distinguish plants it greatly simplifies 

 matters to be able to group those which seem to be related ; 

 but we must remember that outward appearance is often de- 

 ceitful, and that plants, like people living under the same 



^ Tnese letters are used to designate calyx (K), corolla (C), anthers (A), 

 Gyncecium (G). 



