14 



longer or shorter periods of unfavourable 

 conditions. 



In suitable soil the spore germinates, growing 

 out into a filmy, heart-shaped plate scarcely 

 one-third of an inch 

 across. This is 

 known as the pro- 

 thallus or prothallium 

 (Fig. 2). It very 

 much resembles a 

 liverwort, but can be 

 distinguished from it 

 by its paler green 

 colour. It lies pros- 

 trate on the soil to 

 which it is attached 

 by a number of 

 root-like processes, 

 rhizoids (Rh.) which are given off from the 

 under-surface. Amongst the rhizoids one can 

 distinguish numerous small projections. These 

 are the male sexual organs, the autheridia 

 (Fig. 2 Anth. and Fig. 3). Each antheridium 

 contains several male sexual cells the sperms 

 (sp.). Near the notch of the heart-shaped 

 prothallus may be seen the female sexual 

 organs the archegonia (Fig. 2 Arch, and Fig. 4). 



KL 



FIG. 2. A prothallium 



(magnified) ; Rh. = Rhizoids ; 



Anth. = Antheridium; Arch. = 



Archegonium. 



