Branched prothallia in the Polypodiaceae* | 
EvizaBetu D. WuIst | 
(WITH FIFTEEN TEXT FIGURES) 
INTRODUCTION 
Branching in the early stages of the gametophytes of the 
Polypodiaceae has received little attention in the literature. 
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 
(to), 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 (’o2). 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 Polypodium 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 opomancail 
thread like the arms of the letter T, each arm bearing a prothallium. 
In another case observed the young prothallium pr oduced nearly 
colourless protonemal threads from marginal cells. Each of these 
threads bore a prothallium, and in turn produced marginal threads 
* Contribution from the Osborn Botanical Laboratory. 
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