THE FERN BULLETIN 



s: 



little volcano-like protuberances, each containing a 

 single ovule or egg cell, and may be called egg-pits ; 

 the other kind are tiny sacs which contain liquid full 

 of actively moving spiral filaments (beset with vibrat- 

 ing hairs or cells), resembling in essential character 

 the spermatozoa or motile sperm filaments of animals ; 

 they are the sperm-sacs ! The excessively minute mi- 

 croscopic motile "sperms" escape by the bursting of the 

 sacs, and swim through the film of water on the sur- 

 face of the "prothallus." When one of these micros- 

 copic sperm-screws thus arrives at one of the volcano- 

 like egg-pits, it plunges into its opening and fuses 

 with the contained egg cell, thus fertilising it. It is 

 then, and not until then, that the egg cell commences 

 to grow and divide, and gives rise to the young fern 

 plant. The fern plant nourishes itself and develops 

 rapidly, whilst the little green prothallus, having 

 borne its crop of eggs and sperms, withers, and is seen 

 no more. The fern plant on attaining full size and ma- 

 turity produces, as did its grandparents, spore cases 

 on the back of its leaves, which in due time shed their 

 minute unicellular spores, and these falling on the 

 moist earih grow, without any "fertilization" by pol- 

 len or sperm, into marchantia-like prothalli. Thus 

 there are two distinct generations in the life history 

 of the fern. The first is the large foliaceons plant with 

 stem and foliage, which we call a fern. It produces 

 spores of only one kind ; they are self-sufficient, and 

 germinate without any fusion with, or fertilisation by, 

 sperm or pollen. This generation — the fern plant — 

 we call "the spore-bearer," or sexless generation. The 

 second generation is the little flat prothallus which 

 arises from the spores of the spore-bearer. It — and 

 this is the remarkable thing which so long escaped the 

 observation of botanists — produces male and female 



