306 =§ Prof. Lnveing, On Solution and Crystallization. [Nov. 26, 
young plants may die, or are weakly and feeble. It would thus 
appear that the use of the constriction above mentioned is to keep 
the cotyledon closely pressed to the endosperm so that the latter 
may be transferred to the young plant ;—for the excessive elonga- 
tion above mentioned would ensure this. The small diameter of 
the hole acts therefore as a resistance and directs the growth of the 
young plant. Seeds buried in the soil do not shew this markedly 
because the soil naturally offers some resistance to the cotyledon. 
A similar constriction is found in the germination of the Date- 
Palm. 
(6) On the protection afforded by the stipules to the buds of 
Betula Nana. By M. C. Potter, M.A., Peterhouse. 
November 26, 1888. 
Mr J. W. CLARK, PRESIDENT, IN THE CHAIR. 
The following communications were made: 
(1) On Solution and Crystallization, Part 1. By Professor 
LIVEING. 
Abstract. 
In this paper the author gives a physical explanation of the 
causes of the molecular arrangements which give rise, as was 
shewn in the former paper on this subject, to the external forms 
and cleavages of crystals. No peculiar force is required to pro- 
duce these arrangements of the molecules provided they attract 
each other. The supposition made is that while the parts of 
the molecules are in constant motion, the excursions of the parts 
of each molecule from its centre of mass are limited in the solid 
state. The extent of these excursions will in general be different 
in different directions, so that the molecule will on the average 
be comprised within an ellipsoid. For the same kind of matter 
it is supposed that these ellipsoids are all similar and equal. 
If the molecules attract one another, the problem of their ar- 
rangement in stable equilibrium becomes the problem of packing 
the greatest number of similar and equal ellipsoids in a given 
volume. The solution of this problem is given, and it is shewn 
that the ellipsoids will be all similarly situated, though the 
orientation of their axes is a matter of indifference. The matter 
of each molecule will not in general be uniformly distributed 
within the molecular volume, and if in any case it be chiefly 
massed about a particular plane or a particular line, this massing 
