32^ PLANT STUDIES 



and archegonia appear, so that it is evidently a gameto- 

 pliyte. This gametoplayte escapes ordinary attention, as it 

 is usually very small, and lies prostrate upon the substra- 

 tum. It has received the name iri-iAhalliuiii or pi'oth allium, 

 so that v;\\eii the term prothallium is used the gametop)hyte 

 of Ptoridophytes is generally referred to ; just as when the 

 term sporogouium is used the sjjorophyte of the Bryophytes 

 is referred to. Within an archegonium borne upon this little 

 prothallium an oospore is formed. \\'licu the oospore ger- 



inm of a common fern i A-yidhim): A. ^fnrral sui-facc 

 anlliiTidia l(//o. and arclK-uonia uif} : IJ. \cntial surface o1 

 slinwing rhizoids {/■h} and young sporopliytu with root {iv 



HENCK. 



sliowing 

 an old.T 

 and leaf 



minates it develops the large leafy plant ordiiuirily spoken 

 of as "the fern," with its suliterranean stem, from which 

 roots descend, and from which large branching leaves rise 

 above the surface of the ground (Fig. 203, /I). It is in 

 this complex body that the vascular system a|)])ears. A'o 

 sex organs are developed upon it, but the leaves bear numer- 

 ous sporangia full of asexual spores. Tliis complex vascular 

 plant, therefore, is a sporophyti', and corres])(inds in this 

 life history to the sporogonium of the ISryophytes. This 



