52 FERNS. 



their colours. Moreover, the cells of the prothallium 

 resemble those of the parenchyma of a leaf, the epi- 

 dermis with its wavy-margined cells being absent. 



When the prothallium has attained its full develop- 

 ment, minute scattered protrusions from its cells occur 

 on the margin or under surface, resembling short and 

 blunt hairs ; and each of these becomes partitioned 

 off to form a new cell, within which a number of 

 crowded smaller cells are produced. These organs are 

 called antherid'ia (anther, and etSo?, resemblance) ; and 

 within each of the crowded smaller cells is contained 

 a very minute, colourless, coiled fibre, furnished with 

 still finer filaments, called cilia (cilium, an eyelash) ; 

 the ciliated fibres being termed spermatozo' a (crTrepfjia, 

 seed, foSov, animal). At a later period, other organs 

 are found also on the back of the prothallium. These 

 are larger than the antheridia, and are composed of 

 several cells, arranged around a central canal which 

 leads to an embryo- cell situated at its base (PI. II. 

 fig. 2). These organs are the archegonia (apxrj, be- 

 ginning, 7ovo9, offspring). When the antheridia are 

 ripe, they discharge the spermatozoa, which are 

 enabled to swim about by means of their cilia in 

 water (rain), and entering the canal, reach the embryo- 

 cell, which thus becomes fertilized. When fertilized, 

 the embryo-cells produce the little fronds which after- 

 wards grow into the mature plants. 



Hence the spores of ferns differ strikingly from the 

 seeds of the higher plants in not containing the em- 

 bryo radicle and cotyledons already formed, these 

 being produced during or after germination ; also in 

 the fertilizing organs, viz. the antheridia or represen- 

 tatives of the anthers, and the archegonia or the re- 

 presentatives of the pistils, being produced from the 

 cells of the prothallium. 



The more minute of these structures are too diffi- 

 cult of observation and preparation for any one un- 

 accustomed to microscopic manipulation, so that they 



