CHANGES INDUCED IN FLOWER STALKS 303 



cutting are most marked examples of the effort of a plant to re- 

 adjust itself to changes by means of its correlating mechanism. 

 The polarity of plants, by which one end of the axis is constituted 

 the apex of the shoot, and the other the root-bearing end, is also a 

 correlation by which the apical end shows a tendency to bear 

 leaves and give rise to branches while the other gives rise to ab- 

 sorbing organs. This polarity is resident even in fragments of a 

 plant, and roots in certain instances tend to form shoots from the 

 original upper end, and new roots from the end farthest away 

 from the original stem apex. This polarity not only extends to 

 the longitudinal organization of the axis of the plant, but also to 

 the radial arrangement of its organs. 1 



386. Development of Latent Organs as a Result of Correlative 

 Stimulation. Cultivate a number of seedlings of any common 

 herbaceous form and when a few cm. in height cut off the epi- 

 cotyl just above the cotyledons. The buds in the axils of the 

 cotyledons will be awakened and begin development. 



387. Changes Induced in Flower Stalks by Fertilization. Cul- 

 tivate a number of specimens of Arisaema, Cucurbita, or other 

 convenient plant. As soon as the flower buds open, remove sta- 

 mens and enclose in paper bags to prevent pollination. Secure 

 the transference of pollen to the stigmas of others left open. 

 Note the consequent difference in the development of the ovarial 

 tissues and the scapes or peduncles. It will be of interest also to 

 enclose a third lot in paper bags, and to irritate the stigmatic sur- 

 faces by rubbing lightly with a soft piece of wood, or applying 

 1 per-cent. solutions of various salts, such as magnesium chlo- 

 ride, or potassium nitrate and note results. 



If Arisaema is used in the above experiment a specimen may 

 be enclosed in a paper bag and pollen applied with a camel's 

 hair brush to some of the pistils only, which will allow the 

 growth of pollinated and unpollinated ovaries to be compared. 2 



1 Vochting, H. Ueber Organbildung im Pflanzenreiche. 1 : 1878. 

 Reinke, J. Die Abhangigkeit der Blattentwickelung von der Bewurzelung. 

 Ber. Deut. Bot. Ges. 2 : 376. 1884. 



2 Goebel, K. Organography. 1 : 269-270. 1900. 



