166 Gardner—Studies on Growth and Cell 
increased growth. From the tables can readily be seen the 
increase in growth of the roots, in solutions of one-fifth, one- 
tenth and one-twentieth per cent above the control. 
HCl.—Seedlings will germinate, but will live, for only a 
comparatively short time in solutions of HCl of one or two 
per cent. The neutral point is reached at a one-half per cent 
solution. All weaker solutions such as one-fourth per cent, 
one-fifth per cent, one-tenth per cent act as stimulants. 
(W/7,),CO;.—In using (NH,),CO, it was found that only when 
very weak solutions were used, was it possible to obtain any 
results. Germination never occurred in solution of one-half 
per cent, or one-fourth or even one-tenth per cent. Seeds 
germinate and live in a one-thirtieth per cent solution, yet this 
growth is a retarded one. The neutral point is reached in 
solution of about one-fiftieth per cent and all weaker solutions 
act as stimulants. One seventy-fifth per cent and one one- 
hundreth per cent were used, both causing a marked increase 
in growth. 
So we must conclude that it is possible to obtain chemical 
solutions of such a strength that they act as nutritive stimu- 
lants, causing an acceleration in the growth—also to find the 
points of these same solutions which can be regarded as 
neutral, and above which point these solutions have a toxic 
or retarding action. 
C. CEtt DIvISsION. 
Within the past thirty years cell division has been a favorite 
study for cytologists. There has always been much difference 
of opinion amongst writers as to what is the correct explana- 
tion of their observations. Before stating my own observa- 
tions and conclusions, a short review of the more recent 
papers will be given from which can be seen how greatly 
authors differ on the subject. 
A valuable cytological paper which reviews and condenses 
