THE AMERICAN BOTANIST. 



Fig. 11. 



immature At b is shown the same parts, but with sta- 

 mens w'ithering and stigmas read3^ to receive pollen. 



The great composite family 

 to v^hich the asters, sunflowers, 

 goldenrods and their allies be- 

 long, make use of this method, 

 but with the following unique 

 modification : In this family the 

 stamens are joined into a tube 

 by their anthers which open 

 within so that at maturity the 

 pollen falls into this tube. Now 

 at the bottom of the tube lies the pistil but it escapes pol- 

 lenation because its two stigmas are folded face to face. 

 As the pollen is shed, however, the style begins to lengthen, 

 carrying the folded stigmas up through the tube and 

 brushing all the pollen out at the top (Fig. 12 a.) Then, 

 the stigmas spread out, (Fig. 12 h.) the stamens are with- 

 drav^n into the carolla and the pistils are ready for their 

 share of pollen which comes, of course, from some adja- 

 cent flower. This process may be seen very clearly in the 

 common garden sunflower. 



The fact that many flowers find it necessary to obtain 

 their pollen from others has given gardeners a hint which 

 they have been quick to improve upon in the production 

 of numerous hybrids. All that 

 is necessary' is to carefullj^ pick 

 out the stamens of desirable 

 flowers and then pollenate them 

 with pollen from the blossoms 

 with which it is wished to cross 

 them. It is to be understood, of 

 course, that crossing is possible 

 only with closely related plants. 

 Petunias, for example, could not 

 be crossed v^ith geraniums, or 

 lilies with roses, otherwise there would be no distinct 

 types of flowers. Nature has set her ban on such mixing 



Fig. 12. 



