Although the 'soil-less' mix and the fertilization schedule indicated in the C-Fern Manual work reasonably well for general culture of sporophytes, it is likely that modifications could enhance sporophyte growth under greenhouse conditions. Recently, Dr. Jody Banks of Purdue University has found that sporophytes grow very well in straight Indiana topsoil. When tested under greenhouse conditions in Knoxville, we found that Indiana topsoil does indeed promote vigorous growth of young sporophytes. We also tested 50:50 mixtures of this topsoil and the standard soil-less mix, along with Tennessee river bottom soil, straight, and in a 50:50 mix. In all cases the Indiana topsoil gave superior results, at least in short term culture (2-4 weeks), and the 50:50 mixes were somewhat better than the straight soil-less mix. Soil composition is inherently complex and it is difficult to identify specific reasons for the enhanced growth. One factor could be pH -- the pH of Indiana topsoil was ca. 7.5 while the soil-less mix was just below pH 6.0. The 50:50 mixes and the Tennessee soil were intermediate. Another likely factor is nutrient composition. The Indiana soil is from an agricultural region and is no doubt heavily fertilized and limed. Similar agricultural soils from different geographic regions might give similar result. In fact, early attempts to culture Ceratopteris using a mixture of Mississippi agricultural soil, peat and sand were quite successful (Hickok, unpublished). Until the composition and fertilization schedule of the soil-less mix are further optimized, it would be worthwhile to determine if a local topsoil source would enhance growth under specific regional conditions.