

THE FLOWER SHOOT 145 



called). There are thus as many placentse on the walls (pari- 

 etal placentae) of the ovary as there are carpel-leaves in its 

 structure. Examples are seen in the violet, bloodroot, etc. 



b. Free central placenta. Here there is a cloumn of tissue 

 rising in the center of the locule which bears the ovules, as in the 

 pinks, chickweeds, etc. 



2. The compound pistil with two or more locules. Here the 

 edges of the adjacent carpel-leaves are joined together, as in the 

 simple pistil forming the ovule-bearing line along the inner side 

 of the locule, and the sides of each adjacent carpel are also joined 

 where they come in contact, thus forming as many locules, each 

 with its independent placenta, as there are carpel-leaves. The 

 placentae thus form an axis (axih placenta) in the ovary, from 

 which radiate the partitions (dissepiments) separating the locules. 

 Examples are seen in the lily, trillium, etc. 



All gradations exist between the two types of compound pistils, 

 and many of those with a free central placenta are formed from 

 the second type by the disappearance of the partitions. 



229. Kinds of flowers. A complete flower contains all the 

 four series of parts (calyx, corolla, stamens and pistil). When 

 any one series of parts is lacking, the flower is incomplete. Where 

 only one series of the floral envelope is present the flowers are 

 apetalous (petals absent; examples, elm, buckwheat, etc.). 

 Flowers which lack both floral envelopes are naked. When pistils 

 are absent but stamens are present, the flowers are staminate 

 (whether floral envelopes are present or not) ; and so when stamens 

 are absent and pistils present the flower is pistillate. When both 

 stamens and pistils are absent the flower is sterile or neutral 

 (snowball, marginal or showy flowers in hydrangea). Flowers 

 with both stamens and pistils (whether the floral envelopes are 

 present or absent) are perfect (hermaphrodite) ; if only one of 

 these sets of essential parts of the flower are present the flower 

 is imperfect (diclinous). When both kinds of imperfect flowers 

 (staminate and pistillate) are on the same individual plant, the 

 plant is monoecious (of one household). When staminate flowers 

 are on certain individual plants, and pistillate flowers of the same 



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