The number of spines on the pollen surface and the size of pollen grains in the subfamily Asteroideae (family: Asteraceae) were examined for their application in forensic investigations. Gold-coated and un-oriented pollen specimens were observed under a scanning electron microscope. The number of spines per pollen grain varied from 19 to 133, and this number was similar among the species belonging to the same genus, although it highly differed within the same subtribe. With several exceptions, the maximum deviation in the number of spines from the average number was approximately ≤ 20% within each species. This result was consistent with results reported in previous studies and those obtained in an experiment performed using images. These results indicate that the microscopic examination of un-oriented pollen specimens is useful in forensic investigations because preparing and observing oriented specimens are very challenging with a limited sample amount. The size of pollen grains was between 17 µm and 42 µm and was most commonly around 30 µm. Results obtained by plotting the number of spines and the size of pollen demonstrated that these characteristics are possibly useful indicators for forensic discrimination, although additional studies for estimating variations within species are necessary for identification by using the method.
https://ror.org/03g9ek587 
