A study of mycorhizal associations in two species of BotrychiumThe objectives of this study were to examine and describe the mycorhizae associated with Botrychium dissectum and Botrychium virginianum. The objectives also included trying to isolate the fungi associated with them and to analyze the association. Root sections were cleared and stained by placing them in a saturated solution of chloral hydrate and .01% acid funchsin. These sections were either boiled for fifteen minutes or allowed to stand in the solution for at least two days. Hand sections were mounted in glycerine. Examination of these sections showed fungi to be present in the younger roots of B. dissectum and in smaller amounts in all of the roots of B. virginianum. Infection occurred through the epidermis by aseptate, multinucleate hyphae which penetrated to the fourth cell layer of the cortex. Hyphenknauel (hyphal coils) were found in this area. Within the fifth and sixth cortical layers of both species were Pilzverdauungszellen (fungal digesting cells) and sporangioles. Vesicles were observed only in B. virginianum. Following the initial infecting, no hyphal connections to the epidermis were present. The infecting hyphae were irregular varying in diameter from 4 to 12 microns in B. dissectum and from 2.5 microns in B. virginianum. Swellings often occurred in hyphae where they passed through cell walls of the roots. In B. virginianum these swellings were often dark colored. Septations were seen in hyphae on the outside of the roots of B. virginianum. None were observed in the hyphae within the roots. Because of the size differences and habit of growth of fungi within the two ferns, it is proposed that different fungi infect them. Thin sections of roots were surface sterilized and placed upon Czapek's and malt extract media. Fungal isolates from these were compared to fungi seen within the roots. Since no reproductive structures were observed in the hyphae within the roots and all comparisons had to be made with somatic hyphae, identification of the fungi was not possible. Several methods of spore germination were tried. Since these were not successful and since no gametophytes were found, no studies of the reported endophytic fungi could be made.