Birbal Sahni. 
149 
I cannot close this brief account of the meetings of Section K, 
without reference to the very interesting visit that some members 
were able to make to the Government Experimental Station at 
Dulacca, where Dr. Jean White and her staff are endeavouring to 
cope with one of the most difficult practical problems of Australia. 
One-fifth of Queensland is said to be under the dominance of the 
terrible pest, Prickly Pear, and its inroads continue at an alarming 
rate. 
Dr. White’s long lines of experimental plots for testing the 
efficacy of different poisons were the admiration of all who saw 
them, and the laboratory attached now makes possible, investiga¬ 
tions into the physiological aspects of their application, so that 
there is every hope that results of considerable economic import¬ 
ance may accrue. 
FOREIGN POLLEN IN THE OVULES OF GINKGO 
AND OF FOSSIL PLANTS. 
By Birbal Sahni, 
Emmanuel College, Cambridge. 
[With Plate II]. 
HILE examining some material of young Ginkgo ovules 
from Montpellier, I was struck by the very frequent 
presence, in the pollen-chamber, of large pollen-grains with two 
wings, very different from the normal unwinged grains of Ginkgo. 1 
Of the ovules investigated, about a dozen in all, no less than eight 
contained these foreign pollen-grains, which are characterised by 
prominent “ wings ” with reticulate markings like those on the 
bladders of pine pollen ; in both microspores and tubes starch- 
grains are abundant (Plate II, Figs. 1, 2, 3,) and in one case two 
evanescent prothallial cells were seen. These features clearly 
indicate the Abietineous nature of the pollen. 
One of the grains has actually put out a tube twice as long as 
its own diameter, and, what is more striking, it appears from Fig. 2 
as if part of the tube had just penetrated the nucellus. The tip 
1 Recently Professor Jeffrey (Bot. Gaz., Vol. 58, 1914, PI. 23, Figs, 7, 8) 
lias called attention to what he describes as wings on the pollen of Ginkgo ; 
I am, however, unable to qonfirm this observation. 
