392 Dasher. — The Mode of Infection by Smut in Sugar-cane. 
canes or back setts ; these setts had therefore old buds, and so the results 
were negative. But in Java, for the experiments which gave positive results, 
setts from immature cane or top setts may have been used, and these setts 
had consequently tender eyes. The Poona results may be explained in the 
same way, but unfortunately Ajrekar’s experiments are not convincing. 
From his Experiment No. 2 we find that healthy setts unsteeped (plot 
No. 2) gave 122 smutted shoots and diseased setts, unsteeped (plot No. 4) 
gave 228 smutted shoots. No explanation is given as to how healthy setts 
became smutted to such a large extent. Again, in Experiment No. 4, 
25 setts (plot No. 2), first smeared with spores and then steeped in 1 per 
cent, copper sulphate solution, gave only 25 smutted shoots, while plot 
No. 3, a duplicate of plot No. 2 in all respects, gave over 500 smutted 
shoots. It is difficult to explain the disparity between the results of those 
two plots, and therefore the value of the whole experiment is vitiated ; and 
consequently from his experiments it cannot be definitely concluded ‘ infec- 
tion by spores adhering to setts takes place 
Inoculation Experiments. 
For the inoculations either fresh spores were used or cultures grown on 
bread paste. This medium has been found to be very suitable for germi- 
nating smut spores. In twenty-four hours a thin white film of mycelium 
containing innumerable sporidia are found where spores have been planted. 
The infection through sporidia takes place naturally more quickly than with 
spores. 
Unless where otherwise stated, cuttings and plants of the susceptible 
‘ thin ’ varieties, Seretha and Mungo, have been used for inoculations. 
Inoculations on the cut ends of the setts and on the top of the crown, 
rut back without damaging the growing-point, have been unsuccessful. 
Several attempts have been made to infect the cut ends of the setts, but all 
have so far proved unsuccessful. These setts were kept in moist chambers. 
Infection of rootlets and root buds of setts kept in moist chambers have 
also proved unsuccessful. Setts incubated in moist chambers have been 
successfully inoculated through tender buds, the scale leaves of which had 
not turned brown. In some cases the infection takes so readily that in four 
days’ time the mycelium reaches the growing-point (Fig. 2). Old buds 
which have become swollen and the scale leaves of which are hard and 
brown could only be inoculated when wounded. The wound did not reach 
the growing-point, but only slightly exposed the inner tender pale green 
scale leaves. All these experiments were microscopically controlled. The 
control setts invariably remained healthy. 
The inoculations of setts done under moist-chamber conditions were 
duplicated on potted plants. 
Some of the experiments are detailed below. 
