Maybe its only Chaff you have there, as there is plenty of it inside a gum nut. If you really want a special species just plant the seed, I find some veggie seeds are a lot smaller than Eucalyptus and they come up ok, so plant a lot there are so many in one gum nut. Most Eucalypt seeds are small. Have a look at the link below it may help..Cheers..MM.

Here is a link that might be useful: Eucalypt seed

Sometimes the information you need is available in those old-fashioned things called BOOKS!

"Eucalyptus Seed" by Boland & al. (CSIRO 1980) has a mass of data on this subject, with macro photographs of both seed and chaff of a wide range of species plus tables of seed characteristics of a much larger number, including numbers of seed per 10 g, germination times and optimum temps or stratification for cool-climate spp.

If you have access to a major library you may be able to access this book.

Debate is raging in taxonomic circles as to whether Eucalyptus should be slpit further into the (currently informal) subgenera symphyomyrtus and monocalyptus(eucalyptus). One of the distinguishing features is the seed. That of the monocalypts is much larger and generally the same size as the chaff. That of the symphyomyrtus are smaller and are easy to pick from the chaff using a good bench magnafying glass and set of tweesers. I find it best to propagate eucalypts (both subgenera) in trays and transplant to separate containers when about the third or fourth set of seedling leaves appears.