374 



THE QUARTERLY REVIEW OF BIOLOGY 



undergo all degrees of shock and recovery. 

 There is the temporary change with 

 complete recovery; there is the temporary 

 change with temporary recovery, fol- 

 lowed by a recurrence of the new feature. 

 There is the temporary change with a slow 

 recovery; there is the change with slight 

 permanent effect; there is the change with 

 marked permanent effect. There is the 

 change which becomes progressively more 

 and more removed from the original type, 



and finally there is a complete upset of 

 balance. Such is the response which root 

 hairs give to changed environment; it is 

 also the response which all living things 

 are likely to give in a greater or less degree 

 to sudden alteration of their surroundings, 

 and even serves to indicate that the 

 responses obtained in human beings to 

 extreme conditions such as shell-shock, 

 etc., are merely expressions of a fundamen- 

 tal property of protoplasm. 



LIST OF LITERATURE 



(i) Addoms, Ruth M. 1913. The effect of the hy- 

 drogen ion on the protoplasm of the root hairs 

 of wheat. Amer. Jour. Bot., 10: xn-xxo. 



(x) . 192.7. Toxicity as evidenced by 



changes in the protoplasmic structure of root 

 hairs of wheat. Amer. Jour. Bot., 14: 147- 

 165. 



(3) Bardell, E. 1915. The production of root 



hairs in water. Univ. Washington Publ. 

 Botany, 1: 1-19. 



(4) Costantin, M. J. 1885. Recherches sur l'in- 



fluence qu'exerce le milieu sur la structure des 

 racines. Ann. d. Sci. Nat., VII, 1: 135-181. 



(5) Coupin, H. 1917. Influence des sels de cal- 



cium sur les poils absorbants des racines. 

 Compt. Rend. Acad. Sci. Paris, 164: 641-643. 



(6) . 1919. Sur le pouvoir absorbant du 



sommet des racines. Compt. Rend. Acad. 

 Sci. Paris, 168: 519-5x1. 



(7) Cowles, H. C. 1911. Ecology. Vol. x, 



A Textbook of Botany, Coulter, Barnes and 

 Cowles. American Book Co., N. Y. 



(8) Devaux, H. 1888. De Taction de la lumiere 



sur les racines croissant dans l'eau. Bui. 

 Soc. Bot. France, 35: 305-308. 



(9) . 1 891. Croissance des poils radicaux. 



Bui. Soc. Bot. France, 38: 51-52.. 

 (10) Farr, C. H. 1914. Cellular interaction be- 

 tween host and parasite. Phytopathology, 



M: 575-579- 

 (11) . 1915 . Root hair elongation in Knop's 



solution and in tap water. Amer. Jour. 



Bot., 12.: 372.-383 

 (ix) . 1915 . The formation of root hairs in 



water. Proc. Iowa Acad. Sci., 31: 157-165. 

 (13) . 1917. The isoelectric point and the 



median minimum of growth. Proc. Soc. 



Exper. Biol, and Med., 24: 715-716. 



(14) Farr, C. H. 1917. Studies on the growth of 

 root hairs in solutions. I. The problem, pre- 

 vious work, and procedure. Amer. Jour. 

 Bot., 14: 446-456. 



(15) . 19x7. Ibid. II. The effect of con- 

 centrations of calcium nitrate. Amer. Jour. 

 Bot., 14: 497-5 J 5- 



(16) . 19x7. Ibid. III. The effects of con- 

 centrations of CaCU and Ca(OH)2. Amer. 

 Jour. Bot., 14: 553-564. 



(17) . 19x8. Ibid. IV. The pH-moIar-rate 



relation for calcium chloride. Amer. Jour. 

 Bot., 15: 6-31. 



(18) . 19x8. Ibid. V. Root hair elongation 



as an index of root development. Amer. Jour. 

 Bot., 15: 103-113. 



(19) . 19x8. Ibid. VI. Structural respon- 

 ses to toxic pH and molar concentrations of 

 CaCl2. Amer. Jour. Bot., 15: 171-178. 



(10) . 19x8. Ibid. VII. Further investiga- 

 tions upon collards in calcium hydroxide. 

 Bull. Torrey Bot. Club. In press. 



Cxi) . 19x8. Ibid. VIII. Structural and 



intracellular features of collards in calcium 

 nitrate. Bui. Torrey Bot. Club. In press. 



(xx) . 19x8. Ibid. IX. The pH-molar-rate 



relation for collards in calcium nitrate. Ann. 

 Mo. Bot. Garden. In press. 



(X3) . 19x8. The effect of Ca and H ions 



upon root hair growth. Proc. First Intern. 

 Congress Soil Science, 1917. In press. 



(14) . 19x7. The elongation of root hairs 



in solutions of single calcium compounds. 

 A comparison of three anions: nitrate, 

 chloride, and hydroxide, (abstracts only) 

 Amer. Jour. Bot., 14: 6x7. 



(X5) Farr, Wanda K. 19x7. The elongation of 

 root hairs in solutions of single calcium com- 





