THE FLOWER — ITS PARTS AND FORMS 



137 



weed (Fig. 179), smartweed, buckwheat, elm are 

 examples. 



Some flowers lack the pistils : these are stami- 

 nate, whether the envelopes are missing or not. 

 Others lack the stamens : these are pistillate. 

 Others have neither stamens nor pistils: these 

 are sterile (snowball and hydrangea). Those 

 that have both stamens and pistils are per- 

 fect, whether or not the envelopes are missing. 



Those that lack 

 either stamens or 

 pistils are imper- 

 fect or diclinous. 

 Staminate and 

 pistillate flowers 

 are imperfect or 

 diclinous. 



When staminate and pistillate flowers are borne on the 

 same plant, e.g. oak (Fig. 180), corn, 

 beech, chestnut, hazel, walnut, hickory, 

 pine, begonia (Fig. 181), watermelon. 



Fig. 179. — KNOTWEED, a very common but inconspicu- 

 ous plant along hard walks and roads. Two flowers, 

 enlarged, are shown at the right. These flowers are 

 very small and borne in the axils of the leaves. 



Fig, 180. — Staminate Catkins of 

 Oak. The pistillate flowers are in the 

 leaf axils, and not shown in this pic- 

 ture. 



Fig. 181.— Begonia 

 Flowers. 



Staminate at A \ pistil- 

 late below, with the 

 winged ovary at B, 



