100 



FERN-SEED 



mould on to which they have been shed by the fera 

 When the Httle thread is about an eighth of an inch long, 

 and consists of some half dozen cells arranged in a row, 

 the front cells divide, not transversely, but parallel to the 

 length of the thread (Fig. 7, d), and this mode of growth 

 and division, combined with the transversal one, continues 

 until a little green plate or flat expansion consisting of 



S.C 



Fig. 7. — Germination of the spore of a fern. A. A single spore 

 about -jjisth of an inch in diameter. B. The protoplasm bursts 

 from the spore-coat, S.C, and sends out a iilament-like growth, T. 

 In the third drawing, marked c, this becomes a rooting filament, 

 and the rest has divided into five cells, 1-5, containing chloro- 

 phyll grains. D. The front cells are now dividing laterally as well 

 as transversely, e. The prothallus or Marchantia-like growth, 

 twice the natural diameter. 



conjoined cells is produced of about half the size of a 

 threepenny piece (e). It is not circular, but more or less 

 heart-shaped or bilobed. This curious little growth must 

 have a name. It is called the " prothallus " of the fern, or 

 sometimes — on account of its resemblance to the encrusta- 

 tions formed on damp rocks and ditch-walls by the little 



