THE ANGIOSPERM FLOWER 



377 



the bud. The perianth, as a rule, gives the characters of color 

 and form which in popular usage define a flower. It is a very 

 important accession, for it has 

 resulted in some remarkable 

 adaptations and devices on the 

 part of the plant to insure pol- 

 lination by the visits of insects 

 (see Chapter xxxn). The struc- 

 ture of the perianth, with its 

 parts, sepals and petals, 

 is described in Chapter xm. 

 Besides having the perianth, 

 the angiosperm flower is pecul- 

 iar in that the ovules are not 

 normally exposed on the sur- 

 face of the carpels. This means 

 that the carpels, either singly 

 or in groups, form closed struc- 

 tures, which may be termed 

 ovule cases. The ovule case, 

 generally called the ovary (an 

 unfortunate term, for it does 

 not produce eggs but ovules), 

 bears a receptive surface, 

 termed the stigma, upon which 

 the pollen grains may ger- 

 minate. The stigma may be 

 raised upon a stalk, or style. 

 Ovule case, style, and stigma 

 constitute the pistil (meaning 

 a pestle), which is said to be 

 simple when only a single car- 

 pel is involved, and compound 

 if there is a group of carpels. 

 The various arrangements of 



FIG. 301. The lily (Lilium 

 philadelphic um) 



t, dissected flower, showing the pistil and 

 stamens : p, parts of the perianth which 

 have been cut away ; s, bases of stamens 

 cut off. B< floral diagram : p, perianth, 

 composed of two circles of similar and 

 petal-like parts ; s, stamens, likewise in 

 two circles ; section of ovule case (ovary) 

 shown in the center, composed of three 

 carpels (c) so united as to form three 

 locules containing the ovules 



