46 
Proceedings of the Royal Society of Edinburgh. [Sess. 
IV. — Studies on Periodicity in Plant Growth. Part II : Correla- 
tion in Root and Shoot Growth. By Rosalind Crosse, B.Sc., 
Carnegie Research Fellow, 1912-14. (With Two Plates.) 
(MS. received July 2, 1914. Read February 1, 1915.) 
Part I of this work on Growth Periodicity {Proc. Roy. Soc. Edin., 
vol. xxxiii. Part I (No. 8), p. 85) dealt with the occurrence of a four-day 
periodicity in plant organs and with rhythm in roots. With reference to 
the latter, the following conclusions were deduced from various observations 
made up to that time : — 
1. “ Roots exhibit a periodicity under ordinary conditions of environ- 
ment which differs from that of shoots. 
2. “ Owing to correlation, the root periodicity is affected by changes in 
the root rhythm, but to what extent has yet to be determined.” 
Since then, numerous experiments have been performed to find out 
whether any correlation exists between the growth of the root and the 
shoot, and if so, the nature of such a correlation. 
As far as I know, very little has been done in this connection. 
Kny {Annals of Botany, 1894, vol. vii, pp. 265 et seq.; 1901, xv, p. 613) 
concludes, by a method of amputation, that no correlation exists between 
root and shoot growth ; while Hering (Jahr. f. wiss. Bot, 1896, xxix, p. 132) 
has criticised Kny’s results on technical grounds. 
The immediate purposes of this work were to find the correlation 
between the root and shoot growth, and to verify the presence of a root 
periodicity. 
There is every reason to believe that the root periodicity already 
referred to is very like that of the stem — contrary to the conclusion 
o^iven above. 
Methods. 
A detailed account of the automatic precision apparatus used, and the 
methods employed during this investigation, has already been given in Part I 
(loc. cit, p. 90). Vida f aha seedlings have been used throughout, because of 
their plentiful reserve supply and strong roots and shoots. It is thus 
possible to compare the results of different experiments with one another. 
The records of the growth of the roots and shoots were taken simul- 
