Figure 5 Mature fertile C-Fern sporophyte.

While not as rapid in development as the gametophyte generation, sporophytes readily develop into macroscopic plants with roots and leaves. Unlike many ferns, a C-Fern sporophyte lacks a long-lived horizontal woody rhizome. Instead, it grows very much like an upright annual with erect leaves (fronds) and a short stem. Low-maintenance sporophyte cultures can be established in a simple terrarium (a 2-L plastic drink bottle works fine). The entire life cycle, spore-to-spore, can be completed in less than 90 days.

Versatile and Easy

C-Fern is both student and teacher friendly. Because they are free-living and autotrophic, both gametophytes and sporophytes can be cultured on a simple inorganic medium. Easy and foolproof sterile culture techniques are available for gametophyte cultures, and all stages can be conveniently cultured and manipulated with minimal training and equipment.

Getting started can be as easy as boiling water. Pour pre-made C-Fern Basic Medium directly into sterile petri dishes after heating it in a boiling-water bath. C-Fern spores are available in presterilized, premeasured units, and cultures can be inoculated by simply adding sterile water and dispensing the spores onto nutrient medium. After inoculation, the cultures are ready to go under the lights to initiate growth and development. Because the basic medium contains no carbon source (e.g., sugar), the likelihood of airborne contamination is greatly reduced.

Gametophyte cultures of C-Fern are easy to maintain. Use a simple fluorescent lighting fixture (Fig. 6) to provide continuous illumination

Figure 6  Student using stereomicroscope and petri dish with fluorescent lighting and culture dome setup in the background.

. By maintaining cultures in closed culture domes (plastic trays with clear covers), distance from the lighting fixture can be adjusted to achieve an optimum temperature within the culture dome of about 28º C (82º F). Culture domes also allow easy handling of a number of cultures, reduce the possibility of contamination, and buffer against changes in room temperature and humidity.

Population Studies and Large Data Sets

The rapid development and small size of gametophytes (0.5 mm to 3 mm at maturity) allows large populations to be cultured within small petri dishes (60 mm). Millions of gametophytes can be cultured in a very small space, allowing for the participation of large numbers of students.

Cultures of hundreds of gametophytes per petri dish allow students to work with populations as well as individuals.  This provides experience in sampling techniques and the statistical treatment of data.  Both quantitative and qualitative data sets (e.g., growth rate, germination rate, population sex ratio) can be obtained during the 2 to 3 weeks of culture in order to familiarize students with data acquisition, manipulation, and presentation. The importance of sample size can be demonstrated in exercises using both class and individual data. At the same time, it is possible to manipulate individual gametophytes so that controlled matings, both self and cross, are easy to accomplish.