154 



PLANT BIOLOGY 



the time for pollination has come. If the bag is slightly moist- 

 ened, it can be puckered more tightly about the stem of the plant. 

 The time required for the stigma to mature varies from several 

 hours to a few days, (c} When the stigma is ready, an unopened 

 anther from the desired flower is crushed on the ringer nail or a 

 knife blade, and the pollen is rubbed on the stigma by means of a 

 tiny brush, the point of a knife blade, or a sliver of wood. The 



\ 



FIG. 208. A PAPER BAG, 

 with string inserted. 



FIG. 209. THE BAG TIED 

 OVER A FLOWER. 



flower is again covered with the bag, which is allowed to remain 

 for several days until all danger of other pollination is past. Care 

 must be taken completely to cover the stigmatic surface with 

 pollen, if possible. The seeds produced by a crossed flower pro- 

 duce hybrids, or plants having parents belonging to different 

 varieties or species. 165. One of the means of securing new 

 forms of plants is by making hybrids. Why ? 



FIG. 210. FIG. The fig is a hollow torus with flowers borne on the inside, 

 and pollinated by insects that enter at the apex. 



