Foreign Pollen in Fossil Seeds. 
221 
During the last twelve years hundreds of palaeozoic fossil seeds 
must have passed through my hands and it is surprising to find how 
rare is the occurrence of mixed pollen in the pollen chamber. 
What has always impressed me, with cumulative effect, has been 
the purity of the pollen. So far as my experience goes the case of 
Stephanospermum akenioides alluded to by Mr. Salmi 1 remains a 
“ solitary instance” of departure from this rule. Not that puzzling 
objects do not occur in pollen chambers. But in this case alone 
have I felt that the identification of such objects as “ foreign pollen ” 
was reasonably certain. 
On more than one occasion I have remarked on the abundance 
of pollen present in the pollen chambers of fossil seeds. Physostoma 
elegans is pre-eminent in this respect. In my description of this 
seed an instance of the occurrence of nearly fifty grains was recorded. 2 
I have in my possession two other sections of Physostoma worthy 
of mention. One, a transverse section, shews forty pollen grains ; 
the other, median longitudinal, eighty. What is remarkable is that 
the pollen does not seem to be contaminated in either case. 
Curiosity as to the circumstances which brought so much pure 
pollen into these pollen chambers has not been gratified. The 
possibilities may, however, be formulated as follows. In the event 
of aerial transport either the drop mechanism remained in operation 
for a prolonged period or else the pollen was discharged into the 
air at no great distance in dense clouds. Otherwise, some such 
agency of transport as insects must have come into play. 
The latter alternative was in the mind of Sir Joseph Hooker 
when he wrote “ Has anyone accounted for the quantity of pollen 
grains in the sac of the ovule of Cycadese—so many more than the 
wind is likely to have brought ? ” 3 
The suspicion of insect agency has gained a certain amount of 
indirect support from occasional isolated observations on Cycas, 
Welwitschia, etc. Without pursuing this particular matter in detail 
on the present occasion, it is allowable to say that pollen purity is not 
only perfectly consistent with insect agency but is just what might be 
expected in view of the habit commonly attributed to e.g. bees, of 
confining their visits as they go their rounds to a particular species 
of plant. But, apart from its abundance, it cannot be urged that 
1 F. YV. Oliver, Trans. Linn. Soc., Bot., 2 Ser., Vol. VI, p. 376. The 
specimen is now in the Williamson Collection, No. 1486 a, Dept, of Geol., Nat. 
Hist. Museum. 
2 Ann. of Bot., Vol. XXIII, p. 92. 
3 See Oliver & Scott, “ Lagenostoma Lomaxi .” Phil. Trans., B., Vol. 197, 
p. 214, footnote. 
