TEACHERS DEPARTMENT. 
183 
known that an abundance of manure is necessary to induce the 
formation of the “ combs ” in Celosia. A diseased condition may 
result which produces hypertrophied growth and destroys the 
balance of the organ. 
ItAmust be remembered, however, that the environment is not 
the only factor, and that the individual idiosyncrasy of the plant 
must be taken into consideration. 
It is interesting to note in this connection that de Vries has car¬ 
ried out and published the results of a series of experiments show^ 
ing fasciation to be hereditary. A. A. K. 
THE TEACHERS DEPARTMENT. 
Edited by Dr. C. Stuart Gager. 
The Daily Periodicity of Cell-Division and of Elonga¬ 
tion in the Root of Allium.*— It is a well known fact that 
rhythmic variation in the rate of growth in plants is widespread, 
perhaps universal. This rhythm varies in different plants: each 
form seems to have its own peculiar rhythm. Thus far there 
has been little agreement as to the factors involved in the pro¬ 
duction and maintenance of rhythm. Cell-division as a factor 
has been almost entirely overlooked. 
Very little is known of the actual relations between cell-division 
and growth. The object of this study was to determine (I.) 
whether there is a definite daily rhythm in the growth or elonga¬ 
tion of a subterranean part growing under much more uniform 
conditions than the aerial parts ; (II.) whether there is a rhythmic 
daily variation in the rate of cell-division of a growing organ; 
(III.) if such rhythms exist, to determine whether there is any 
correlation between the processes of cell-division and elongation. 
The daily periodicity of cell-division was studied (I.) under 
normal conditions; (II.) with regard to the effects of solutions. 
The tables constructed as a result of measurements and counts 
show how r.emakably similar are the conditions of the root tips 
* Summary of article by W. E. Kellicott in Bull. T. B. C., Oct., 1904. 
