68 
F. STOWARD, D.SC. : 
develop its layer of wound cork as quickly as possible, and 
the more rapidly this takes place, or may be induced, the 
better. 
Again the possibility of infection by both fungous and 
bacterial organisms resident in the soil which are pathogenic 
or disease-producing to the cultivated tuber is always 
existent. The barrier of wound cork must at least be an 
obstacle to the ready entry of these organisms. Its rapid 
formation in some measure amounts to the interposition 
of a first line of defence against invasion. 
1 his view may a fortiori be advanced when we recall 
Myoshi’s experiments of long ago — -experiments confirmed 
and extended by subsequent investigators — which showed 
how slender and artificial is the line of demarcation between 
saprophytic and parasitic organisms. The experimental in- 
jury of a plant tissue, for example a minute wound made 
by puncturing a tissue with a sterilised needle, the intro- 
duction at the point of injury of what were formerly regarded 
as obligate saprophytic organisms, that is, organisms which 
live on dead matter exclusively, and the acquisition of 
parasitic functions by these same organisms, widened the 
highway of plant pathology and indicated a line of enquiry 
into the possible origin and nature of parasitism as ex- 
emplified by the lower fungi. 
The apparently beneficial effect of the treatment of 
cut-sets with air slaked lime is reflected by the planting 
tests. In both series not only did the limed sets (Experi- 
ments i and 5) sprout earlier than the other members of the 
series, but their rate and luxuriance of growth was also 
superior. It does not seem very probable that the com- 
paratively minute amounts of lime introduced with these 
sets could have exercised any direct chemical stimulus, 
although such an influence is not entirely excluded. As 
the accompanying photographic representations (Figs. 9-12) 
of these experimental series taken 38 days after planting 
show , and observation confirms, the comparative luxuriance 
of growth during this period was most advanced in the 
case of the lime-dressed sets. 
These results, taken in conjunction with those given 
in Tables If and III, apparently show that the two chief 
factors are (1) the reduction in the loss of moisture which 
in its turn is dependent on (2) the more rapid formation 
of cork in the case of dressed tuber sets. These experiments 
also furnish a rational explanation of the principle under- 
lying the practice of dressing tuber-sets with substances 
which stimulate the more rapid formation of cork over the 
freshly-cut surfaces of the sets than occurs with the un- 
treated sets. 
