Division in the Root of Vicia Faba. l6i 



total growth takes place between 7.30 a. m. and 5.30 p. m.," 

 or, in short, growth by day exceeds that by night. 



It seems difficult to account for such results as those ob- 

 tained by Sachs. The experiments, performed by the writer, 

 were conducted under perfectly natural environmental con- 

 ditions, and moreover, not one of the results would stand as 

 an exception to the general conclusion. And as proof that no 

 extraneous or mechanical factors could have interfered during 

 the night, are the experiments watched continually during the 

 entire period of twenty-four hours. The latter are in no way 

 different from those in which observations were made during 

 the day until 4 or 5 p. m., and where the night growth was 

 obtained by the reading of the next morning. 



The rate of growth was obtained by measuring the amount 

 of growth during a definite number of hours of the day or 

 night, and calculating from this the rate per hour. Thus, for 

 example, to take the root, recorded on Plate I, Fig. I — here 

 the growth from 10 a. m. to 4 p. m., or for six hours, was 

 13 mm., — a rate of 2^ mm. per hour, and from 4 p. m. to 

 9 a. m. of the following day, — or for a period of 17 hours, — 

 the growth was 1 1 mm., — a rate of \\ mm. per hour. 



From the above experiments and observations, but one 

 conclusion can be drawn, and this, as before mentioned, is the 

 fact that the rate of growth of roots is greater during day thaa 

 during night. 



B. Relative Growth of Roots in Different Chemical 

 Solutions. 



These experiments were performed with a view to ascertain 

 the action of chemical solutions of various strengths on the 

 growth of germinating seedlings. 



Dr. Rodney True ' has recently published some instructive 

 results on the toxic action of acids and salts on seedlings. 



•Toxic Action of Dissolved Salts. R. True. Bot. Gazette, vol. 22, 1896. 



