OF TENNESSEE. 51 



The two great classes of Phsenagamous plants, indicated 

 by this difference of the stem, possess also a marked differ- 

 ence in the structure of their seeds. The embryo of all 

 endogenous plants sprouts with only one cotyledon or seed 

 leaf. Hence they are called Monocotyledonous plants. The 

 embryo of the exogens bears a pair of cotyledons, hence 

 exogens are also called Dicotyledonous plants. 



The Monocotyledons, with a stately assembly of fami- 

 lies, furnish us with the families of the Grasses (graminece) 

 and the Sedge family (Cyperacece) , while the Dicotyledons 

 embrace several families, which constitute more or less val- 

 uable pasturage herbs, but the Leguminous or Pulse family 

 is the most important one, and deserves especial attention. 



It has been stated that Phsenogamous plants possess vis- 

 ible organs of reproduction. When these organs are en- 

 closed within envelopes for their protection, this envelope 

 is called flower. The flower is called complete when the 

 envelope consists of two circles of flowering leaves, the 

 outer and lower one called the calyx, the interior and gen- 

 erally delicately colored one, the corolla. The parts or 

 leaves forming the calyx are termed the sepals, the parts of 

 the corolla petals. The petals, however, are frequently 

 absent when the flower is said to be apetalous, or petals and 

 sepals both wanting, when the flower is called incomplete. 



The essential organs of flowers are likewise of two kinds 

 and disposed in two circles, one including the other. The 

 outer ones are called stamens. A stamen consists of a col- 

 umn or stalk called the filament, to the apex of which is 

 attached a rounded case, called the anther, filled with a 

 powdery substance caljed the pollen, which it at length dis- 

 charges through one or more slits. The remaining seed- 

 bearing organs which occupy the summit of the flower are 

 termed the pistils. A pistil is distinguished into three parts, 

 the ovary, the hollow portions at the base which contains 

 the ovules or bodies destined to become seeds ; the style or 

 columnar prolongation of the apex of the ovary, and tbe 



