4AA SECTIONAL TRANSACTIONS.—K. 
after growth was practically complete. Evidence was obtained indicating that 
the intluence of the ring on the upward movement of nitrogen was independent 
of its effect on the organic content of this part above the ring or on transpiration. 
Experiments with spiral ringing and other special treatments give further 
evidence that foods and nutrients travel upwards and downwards chiefly through 
the phloem. 
(c) Dr. D. F. MacDoucau.—Variations in Volume of and 
Movements of Liquids in Trees. 
Dendrographic measurements of several species of trees show that the trunks 
undergo variations in volume, which may be correlated directly with the transpi- 
ratory activity of green surfaces, which in turn varies with the width of the 
stomatal slits. 
The period in which stomatal slits are widest is one of contraction of the 
trunk : closure of stomata is accompanied or followed by expansion of the 
trunks. Contraction of the trunks or stems of mesophytes and sclerophylls 
takes place in the daytime; contraction of flattened or cylindrical stems of 
cacti takes place at night and expansion in the daytime, in reverse of the 
occurrences in the more general type. 
The time or hour at which these two phases of variation prevail changes 
with the season. At the time of maximum growth contraction in coniferous 
trees may begin within a half-hour after sunrise. 
Such reversible variations are modifiable by changes in relative humidity, by 
defoliation, girdling, topping, or any agency which alters transpiration or rate 
of conduction; and are explainable on the basis of Professor Dixon’s conception 
of the mechanism of the ascent of sap. 
The upward path of moving solutions of a basic dye such as fuchsin is found 
to be in the wood formed within the previous two years; when two layers are 
formed in a season, conduction is chiefly in the ono formed earlier. Whether the 
other layers are more available or suitable for the downward conduction of 
organic material is yet to be tested. 
The amount or reversible variation in the diameter of a young pine may 
be 1 part in 170, in the upper part of a tree approaching maturity 1 part in ~ 
900; in the basal region 1 part in 1700; in a large root 1 part in 364. As this 
variation takes place chiefly in the outer wood, it is found that in such recently 
formed layers the co-efficient of expansion and contraction may be five to ten 
times greater than that of the trunk taken as a whole. as given above. 
(d) Prof. J. H. Priestiey. 
(e) General Discussion. 
Afternoon Excursion to High Park and Humber Valley. 
Friday, August 8. 
2. Presidential Address by Prof. V. H. Bracxman, F.R.S., on 
Physiological Aspects of Parasitism. (Page 233.) 
3. Dr. W. Rosinson.—On the Conditions Controlling Growth and Repro- 
duction in Pyronema confluens. 
The generalisation of Klebs regarding the antithesis between vegetative 
growth and the appearance of reproductive structures in many fungi is found 
to hold for Pyronema confluens. The lateral, aerial branch-systems of hypha 
which give rise to the antheridia and oogonia arise in cultures after vegetative 
extension is checked at the margin of the medium. Whether the branch- 
systems referred to will develop into antheridia and oogonia and subsequently 
apothecia is determined by the composition of the medium, especially as regards 
carbohydrate and nitrogen, by the relations of the culture to light, and by 
the humidity of the atmosphere over the mycelium. No reproductive structures 
arise in the dark, but certain white bodies occur in positions comparable with 
the aerial branch-systems referred to. ‘These white bodies, which are very rich 
