SECTIONAL TRANSACTIONS .—K. 387 
Tuesday, September 11. 
Joint Discussion with Section M (Agriculture, g.v.) on Soil and 
ecological studies in relation to forestry and grazing (10.0). 
Alternative programme for Members not attending the above discussion :— 
Prof. J. Doyie.—Pollination in the conifers, particularly in the 
Abietinee (10.0). 
In conifers the pollination-drop mechanism is much the commonest, 
occurring in the Cupressinex, Callitrinee, Sequoiinee, Taxinez, and 
probably most of the Podocarpinee except Saxegothea, in which the pollen 
germinates on the scale. Germination of the pollen on the scale is also 
now well known as characteristic of the Araucarines. 'The Abietinean 
mechanisms are, however, much more varied. Some of these have been 
briefly referred to previously, but have since been more fully examined and 
- other genera dealt with. In Tsuga the pollen falls on the scales, the long 
- tubes growing like fungal hyphz to the ovules in a manner similar to that 
of the Araucarinee. In Cedrus the pollen, caught by a micropilar flap 
in the autumn, is held there till spring, when the nucellus, rather stigmatic 
at the apex, grows up to make contact with the pollen im situ. The 
mechanism in Pinus, paralleled apparently in Picea and to some extent in 
Abies, is associated with an exudation of fluid.. The micropyle in Pinus 
is extended into two long narrow arms, to which pollen readily adheres. 
At night fluid is secreted, filling the micropilar tube, but in most species 
this fluid is to be found rarely, if at all, in the day period, being reabsorbed 
in the early morning hours. On reaching the level of the arms the fluid 
is drawn out as a film by surface tension up to about half their length. 
The pollen grains, being easily wetted, are quickly drawn into the fluid. 
Immediately after the pollen has been so drawn in, the fluid is reabsorbed 
by the ovule, the pollen being lodged on the nucellus, and the whole micro- 
pyle becoming dry internally within five or, at most,ten minutes. The wings 
on the pollen facilitate its neat lodging on the nucellus. Dichogamy seems 
characteristic of certain species. Picea orientalis appears to be interestingly 
intermediate between the normal Pinus-Picea type and the Larix-Pseudo- 
tsuga type with the large stigmatic swelling of the micropyle edge. 
There are thus in the Abietinez at least four main types of pollination 
mechanism, with additional variations in these. 
Prof. T. M. Harris.—The reproductive organs of the fossil Ginkgoales 
(10.40). 
The only reproductive organs which have been referred to the fossil 
Ginkgoales are a few resembling those of Ginkgo biloba, and none of these 
have been investigated in detail. Comparison of the cuticles of all the 
isolated fructifications and leaves in the lower Jurassic flora of Greenland 
has, however, provided reasons for referring to the Ginkgoales certain 
reproductive organs which differ greatly from those of G. biloba; among 
the male organs Bernettia, hitherto regarded as the female cone of a Cycad, 
and Leptostrobus, hitherto regarded as the female cone of a conifer ; among 
female organs Staphidiophora, a new genus with the appearance of a bunch 
of currants. The bearing of these fossils on Gymnosperm morphology is 
discussed. 
