84 THE BOOK OF NATURE STUDY 



of peat or leaf-mould, and some glass sheets or bell-glasses. If 

 you use flower-pots, half fill the pot with gravel and then put in 

 enough peat to fill the pot to an inch from the top. If seed-pans 

 are used, simply stand a lump of peat in the middle of the pan. 

 In any case, the vessels and the soil must be, as far as possible, 

 " sterilised/' otherwise you will get fungi and other plants which 

 will damage or destroy the germinating spores. Either bake 

 the vessels and soil in a hot oven for a few hours, or steep them 

 in boiling water. If you bake the soil, moisten it, and the pot 

 or pan, and when it is again cold shake some spores over it, and 

 cover with the glass. The latter keeps the soil moist, since the 

 evaporated water condenses and runs back into the vessel, but it 

 is as well to remove the glass now and then to renew the air. The 

 ripe spores will retain their vitality for several months in most 

 cases, but they usually germinate best if sown promptly, and the 

 green spores of Royal Fern and a few others will perish if not 

 sown at once. The pots or pans should be set out of direct sun- 

 light, and the early germination of the spores is hastened by 

 some warmth. The spores may be sown on previously heated or 

 scalded bits of brick or tile sloping into water in a jar or dish, 

 instead of using soil (peat or leaf-mould). In any case, do not 

 sow the spores too thickly, and do not water them from above 

 (for what reasons ?). 



In a few weeks (a few days in the case of the Royal Fern) you 

 will see greenish threads creeping over the soil, with here and 

 there a small green disk. Each spore, on germinating, sends out 

 a colourless thread, which becomes rooted in the soil, and then 

 a thicker green thread which grows along the surface. The 

 green outgrowth gradually broadens at the front, and finally 

 grows into a thin green, heart-shaped plate bearing numerous 

 rooting-hairs on its lower side. The green plate is called the 

 prothallus. The germination of a fern-spore is obviously very 

 different in its results from that of a seed. 



The prothallus is usually more or less heart-shaped in outline, 

 and has a thick opaque middle part (cushion) with thin trans- 

 parent side parts. It is fixed to the soil by numerous fine rooting- 

 hairs which grow chiefly from the cushion. The upper surface is 

 quite even and smooth, but the underside shows, besides the 



