26o 
Brenchley— Organic Plant Poisons . //. 
shoots seemed to live on for some time longer, though probably this was 
merely an external appearance of vitality. They remained green for a fort¬ 
night in the weak nutrients and for nearly three weeks in the strong. The 
phenol exerted an antiseptic action for some long time, in spite of the death 
of the roots, but at last moulds began to form on the surface of the solutions. 
With a lower concentration, M/ioo x J, the difference in the action 
of the poison in strong and weak nutrients was evident from the first. 
With the strong nutrients root growth was apparently quite normal for the 
first few days, after which it was very much hindered, though no constriction 
groxis 
Fig. i. Average dry weights of ten series 
of pea plants grown in strong nutrient solu¬ 
tions in the presence of differing amounts of 
phenol. Sept. 24-Dec. 5, 1914. 
Fig. 2. Average dry weights often series 
of pea plants grown in weak nutrient solu¬ 
tions in the presence of differing amounts of 
phenol. Sept. 24-Dec. 5, 1914. 
or unnatural coloration of roots was manifest. With weak nutrients, on the 
contrary, the roots showed an inclination to be constricted and pink in 
colour near the tips within two days, the tips themselves being dead white 
and somewhat swollen. Later on, in both sets the shoots became very weak 
and the roots bunchy owing to the belated formation above water of laterals 
which showed great reluctance to enter the solutions. After about six 
weeks the roots began to elongate, but the start into activity occurred some 
days earlier in the strong nutrients, the ultimate improvement in the type 
of root being much more marked. 
With the next concentration, M/ico x 1/5 2 , all the plants started off in 
a similar way, with shoots much like those of the control plants and roots 
of a normal type ; gradually there was a falling off in the rate of growth. 
After about three weeks the difference between the sets was more manifest. 
