THE FL O WER PER T I LIZ A TION AND POLLINA TION 1 5 3 



stigmas will receive acceptable pollen to enable the plant to 

 perpetuate its kind. At any time in summer, or even in fall, 

 examine the apple trees carefully to determine whether any dead 

 flowers or flower stalks still remain about the apple ; or, examine 

 any full-blooming plant to see whether any of the flowers fail. 

 153. Keep watch on any plant to see whether insects visit it. 

 What kind? When? What for? 154. Determine whether the 

 calyx serves any purpose in protecting the flower. Very carefully 

 remove the calyx from a bud that is normally exposed to heat 

 and sun and rain, and see whether the flower then fares as well as 

 others. 155. Cover a single flower on its plant with a tiny paper 

 or muslin bag so tightly that no insect can get in. If the flower 

 sets fruit, what do you conclude ? 156. Remove carefully the 

 corolla from a flower nearly ready to open, preferably one that has 

 no other flowers very close to it. Watch for insects. 157. Find 

 the nectar in any flower that you study. 158. Remove the stigma. 

 What happens? 159. Which of the following plants have perfect 

 flowers : pea, bean, pumpkin, cotton, clover, buckwheat, potato, 

 Indian corn, peach, chestnut, hickory, watermelon, sunflower, cab- 

 bage, rose, begonia, geranium, cucumber, calla, willow, cotton- 

 wood, cantaloupe ? What have the others ? 160. On wind- 

 pollinated plants, are either anthers or stigmas more numerous ? 

 161. Are very small colored flowers usually borne singly or in 

 clusters ? 162. Why do rains at blooming time often lessen 

 the fruit crop ? 163. Of what value are bees in orchards ? 

 164. The crossing of plants to improve varieties or to obtain new 

 varieties. It may be desired to perform the operation of polli- 

 nation by hand. In order to insure the most definite results, 

 every effort should be made rightly to apply the pollen which it 

 is desired shall be used, and rigidly to exclude all other pollen. 

 (a) The first requisite is to remove the anthers from the flower 

 which it is proposed to cross, and they must be removed before the 

 pollen has been shed. The flower-bud is therefore opened and the 

 anthers taken out. Cut off the floral envelopes with small, sharp- 

 pointed scissors, then cut out or pull out the anthers, leaving only 

 the pistil untouched ; or merely open the corolla at the end and 

 pull out the anthers with a hook or tweezers ; and this method is 

 often the best one. It is best to delay the operation as long as 

 possible and yet not allow the bud to open (and thereby expose 

 the flower to foreign pollen) nor the anthers to discharge the 

 pollen. (<) The flower must next be covered with a paper bag to 

 prevent the access of pollen (Figs. 208, 209). If the stigma is not 

 receptive at the time (as it usually is not), the desired pollen is 

 not applied at once. The bag may be removed from time to time 

 to allow of examination of the pistil, and when the stigma is 

 mature, which is told by its glutinous or roughened appearance, 



