SECTIONAL TRANSACTIONS.—K. 449 
ledge of geological history as far as it affects these plants. At this point the 
case of Liriodendron, since it epitomises that of the Magnolie, is briefly 
sketched. 
These various aspects of the subject are then brought into harmony, and 
the history of the Magnoliex, as indicated by them, is postulated. The assump- 
tions involved by the Hypothesis of Migrations are reviewed and their logical 
results indicated. Finally, the hypothesis is considered from the point of view 
of its value in helping to elucidate the present distribution of flowering plants 
in general, ard the paper concludes with a comparative valuation of the 
Hypothesis of Migrations and the Hypothesis of Age and Area. 
15. Miss E. R. Saunpers.—The Evolution of the Carpel. 
The current conception that carpels are all of one type representing an 
expanded folded leaf is inadequate and erroneous. Evidence is brought forward 
in disproof of this idea and in support of the view that a general tendency to 
reduction in number accompanied by a process of ‘ consolidation’ has led to 
the evolution of several different carpel types. Polymorphism of this character 
is of almost universal occurrence among flowering plants, and is accompanied 
by separation and redistribution of the three carpellary functions (protective, 
receptive, reproductive). Many assumptions, quite unfounded but inevitable 
from the orthodox standpoint, now become unnecessary. Certain anatomical 
features hitherto devoid of significance acquire new meaning, and numerous 
apparent anomalies for the first time become intelligible and fall into line, as, 
e.g., the commissural stigma, true obdiplostemony, free-central placentation, the 
occurrence of supernumerary styles and stigmas, polymorphic fruits, reversed 
orientation of the gyneceum, and many others. 
16. Prof. D. THopay.—Some Aspects of the Richness of the Cape 
Flora. 
The richness of the Cape Flora is not a simple phenomenon. The following 
_ are factors which may have influenced it :— 
(1) Climatic conditions keep the vegetation more or less open, reduce mutua 
competition, and so favour fuller registration of mutability. : 
(2) Conditions may have led to greater mutability, either through the variety 
of habitats provided or by directly inducing it. This is particularly suggested 
by the concentration of endemic species in the South-West Cape, especially 
large genera like Phylica, Erica, &c., and by the similar richness and endemism 
of the south-west part of West Australia. 
(3) The origin of species has continued relatively undisturbed since Tertiary 
times. No reservoir of cold temperate vegetation exists to the south, and 
hence there has been no parallel to the devastating migrations during the 
Pleistocene in the Northern Hemisphere which must have wiped out particularly 
those species that were most highly specialised and confined. 
17. Prof. F. J. Lewts—The Behaviour of Chloroplasts and other 
Cell-contents at Low Temperature. 
The changes in shape and position of the chloroplasts in the leaf cells of 
species of Picea, Pinus, Abies and Thuja at the Pacific coast are described. 
Comparison is made with the features present in conifers native to Alberta in 
the winter, observations being made on plants outside and others kept at green- 
house temperature. 
The ability of the chlorophyll to carry on carbon assimilation while in the 
winter condition at laboratory temperatures. is discussed on experimental 
evidence. 
18. Joint Discussion with Section M on Forest Problems. 
(a) Mr. J. W. Toumny.—Recent Progress and Trends in Forestry 
in the United States. 
National, state, communal, and private enterprise all enter into recent 
progress in forestry in the United States. National forestry began earlier and 
has gone farther ; state and communal forestry are of later development ; private 
1924 GG 
