526 SECTIONAL TRAN SACTIONS.—M*. 
There is evidence to show that part of this influence is in the stem piece of the 
rootstock, the path by which the materials, collected by the roots, pass to the scion. 
This has been proved by the use of pieces of stock stems used as ‘ intermediates ’ 
between roots and ultimate scion. Workers in America studying the effect of scions 
grafted direct upon seedling roots concluded that stock infiuence lay in the stem 
ortion. 
i Evidence is now presented to show that stock influence is also significantly apparent 
upon two varieties of scion worked directly upon clonal vegetative piece roots in two 
repeated experiments, the trees being three and four years old respectively. The 
influence is apparent in type of growth, early fruit bud formation, percentage of 
blossom setting, amount and quality of fruit, and in maiden growth and weight of 
these trees lifted at two yearsold. Whenexamined at that age there were no significant 
differences caused by scion effect on vegetative piece roots. 
It is shown that, at least up to eight years old, a series of comparable trees of four 
varieties, growing upon their own roots and worked upon vigorous and semi-dwarfing 
stocks, the latter profoundly modify for the fruit growers’ benefit the behaviour of 
the tree on its own roots. In addition, it is pointed out that in this country, the 
obtaining of satisfactory trees on their own roots or bench grafted on seedling roots 
has never been a practical proposition. 
Examples of the practical value of vegetative rootstocks to the fruit grower are 
given, and further evidence is produced which shows that stem worked trees are less 
variable when worked on clonal stocks than when worked on seedlings. 
The influence of vegetative rootstocks has not decreased with years, though the 
relationship between growth and fruiting and the interrelationship of trees on one 
stock and another have, in some cases, as anticipated, been qualified by time. 
Monday, September 28. 
Discussion on Glasshouse Problems :— 
Dr. W. F. Bewiry.—Some Factors which affect the Health of the Tomato 
under Commercial Conditions. 
(1) The total crop produced in any year varies directly with the total number of 
hours of bright sunlight between April 1 and September 30. 
(2) Potash and Nitrogen requirements also vary in accordance with the amount 
of prevailing sunlight. 
(3) Potash is the most important fertiliser and affects the quality of the fruit, 
resistance to certain diseases and power to withstand sudden harmful changes in the 
environment. 
(4) The timely application of Nitrogen and Potash is most important—the plant 
requiring most potash in the early stages of growth and increasing nitrogen as the 
plant ages. 
(5) Correct air and soil temperatures are important. A uniform night tem- 
perature is necessary for maximum crop. Raising the soil temperature by artificial 
devices has given promising results. 
(6) Mosaic disease reduces the crop yield on many commercial nurseries. It can 
be controlled largely by the use of clean seed. 
Dr. O. OwEN.—Carbon Dioxide in relation to Tomato Crops. 
Carbon dioxide in glasshouses under ordinary cultural conditions is irregularly 
distributed throughout the whole atmosphere. The average concentration falls to a 
minimum between 1.30 p.m. and 2.30 p.m. and rises to a maximum at about 5.30 a.m. 
When the concentration of carbon dioxide is increased artificially, the gas may be 
distributed in ascending layers of decreasing concentration, but’ such a distribution 
persists for a very short time only. 
The introduction of excess carbon dioxide into a house is followed by a heavy 
loss of the gas, despite careful attempts to prevent leakage. This loss commences 
