[From the Bui.lbtim of the Tokkrv I'.otanicai. Clue, 43: 365-383. 14 Aug 1916.] 



Branched prothallia in the Polypodiaceae* 



Elizabeth D. Wuist 

 (with fifteen text figures) 



Introduction 



Branching in the early stages of the gametophytes of the 

 Polypodiaceae has received Httle attention in the Hterature. 

 Branching in older prothallia by means of adventitious outgrowths 

 arising from any part of the prothallium has been described for 

 various genera by Wiegand ('49), Hofmeister ('51), Kny ('70), 

 Goebel ('77), De Bary ('78), Bauke ('78), Dodel-Port ('80), 

 Klebs ('93), Heim ('96), Lagerburg ('06), Pace ('10), Heilbronn 

 ('10), Fischer ('11), Schlumberger ('11), Wuist ('13), Pickett ('14), 

 and Black ('15). Few cases have been cited where branching 

 took place at an early period in the development of the gameto- 

 phyte, except in the case of Vittaria which has been described and 

 figured by Britton and Taylor ('02). As it is characteristic of 

 the prothallia of that genus to branch extensively, resembling in 

 this respect the gametophytes of the Hymenophyllaceae, no 

 examples will be cited. Among the other genera of the Poly- 

 podiaceae the following cases of branching, while the prothallia 

 were still in the filamentous stage, have been noted. Beck ('80) 

 described branched prothallia of Scolopendrium vulgare Sm., while 

 Klebs ('93) by means of weak light obtained, in Poly podium aureum 

 L., branched prothallia with adventitious outgrowths. Atkinson 

 ('94) observed "in Adiantum cuneatum . . . some curious forms 

 of starved prothallia," and added: " In one case, first noted by a 

 student, the protonemal thread forked a short distance from the 

 spore, and the branches extended at right angles to the primary 

 thread Hke the arms of the letter T, each arm bearing a prothallium. 

 In another case observed the young prothallium produced nearly 

 colourless protonemal threads from marginal cells. Each of these 

 threads bore a prothallium. and in turn produce d marginal threads 



* Contribution from the Osborn Botanical Laboratory. 



365 



