io6 FERN-SEED 



spore cases on the back of its leaves, which in due time 

 shed their minute unicellular spores, and these falWng on 

 the moist earth grow, without any " fertilisation " by pollen 

 or sperm, into marchantia-like prothalli. Thus there are 

 two distinct generations in the life-history of the fern. 

 The first is the large foliaceous plant with stem and leaves, 

 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 

 reproductive organs — the sperm-sacs and the egg-pits. It, 

 small and obscure though it be, is a complete organism in 

 itself, producing " eggs " or " germ-cells " which are duly 

 fertilised by sperm threads. We call it, in contrast to the 

 first generation, " the egg-and-sperm bearer," or the sexual 

 generation. Each of its fertilised eggs gives rise by 

 growth and development to a spore-bearer or fern. Thus, 

 then, there is an alternation of the two generations, the 

 spore-bearing big fern and the egg-and-sperm-bearing 

 marchantia-like prothallus. After all, our ancestors were 

 right in thinking that something very queer and unusual 

 underlay the propagation of ferns ! Not the least note- 

 worthy fact in the matter is that the male fertilising 

 element of the sexual generation of the fern is not dry, 

 dusty " pollen " as in flowering plants, but microscopic 

 aquatic " spermatozoa " like those of animals. Thereby 

 hangs a tale of extraordinary interest as to the nature and 

 origin of flowering plants to which I will give a new 

 chapter. 



