268 
Brenchley.—Organic Plant Poisons . II. 
Barley (Figs. 9, 10, 11). 
M/100. With 0- and/-cresol root growth was checked almost as soon 
as the plants were put into the solutions, but with ;/z-cresol a little root 
development was made for a few days before growth was inhibited. All 
roots were very white, and no mould appeared in any case. The shoots 
did not develop at all, but the single leaf turned a brownish yellow colour 
and expanded to its fullest extent, contrasting strongly with the usual habit 
of barley shoots, which when poisoned strongly remain rolled up at death. 
M/ioox-l- was very toxic in every case. The shoots were rather less 
Fig. 9. Average dry weights of ten series 
of barley plants grown in strong nutrients in 
the presence of differing amounts of 0-cresol. 
March 8-April 21, 1915. 
I = 
loo § 6 
Fig. 10. Average dry weights of ten series 
of barley plants grown in strong nutrients in 
the presence of differing amounts of m - 
cresol. March 11-April 24, 1915. 
checked, and formed two little leaves, but development did not go beyond 
this. The familiar red coloration due to starvation appeared at the base of 
the stem. By the end of the experiment the plants were all but dead, the 
lowest leaves being deep yellow and the root dying. Mould appeared on 
the roots, being most strongly marked with /-cresol. 
M/ioo x 3/ 5 2 . The greatest differentiation in the action of the cresols 
occurred with this concentration. With <?-cresol the roots were some time 
before they started into growth ; when they did begin to develop, stubby 
laterals were formed. Eventually these began to push down into the solu¬ 
tions, but they, were of a thick type, unlike normal barley roots. The 
