"hanks Gomero for the interesting reference. After trialling many different species I think there are several different processes. As indicated for Acer pseudosieboldianum ssp takesimense, I think the tough middle capsule may be enough to delay germination till it softens. For most early excision doesn't work as I think some chemical changes have to occur at cool temperatures so I give all a period of cold stratification. For many I think germination inhibitors especially around the immature root may be important as they only seem to germinate even when excised if the root is "misted" with water for a time eg Acer nikoense. All seem to germinate quicker if the root especially is exposed. Emery, I plant un-excised seed buried a little but with excised I leave them on the surface so the root can be gently sprayed with a mist ? to wash away inhibitors. The pots are kept in re-sealable plastic bags to keep humidity high in gentle light (see picture). The one flaw of the technique is that some seed lose direction and the roots may need re-directing down. This may happen naturally also and seedlings just get lost. With the technique it doesn't seem to have any long lasting affect"